(FORTUNE Magazine) – The stock market was never like this. Consider: In a brisk four minutes and 26 seconds of bidding this year, Vincent van Gogh's Sunflowers was sold to a Japanese company, Yasuda Fire & Marine Insurance, for $39.9 million, the highest price ever paid for a painting. That March evening at Christie's, the London auction house, may stand as the pinnacle of a decade-long boom in which nearly every kind of art has appreciated dramatically. Helping to oil this boom are some 1,000 corporate collectors who have discovered that painting and sculpture can be assets as valuable as plant and equipment. The best collections usually reflect the interest and taste of a strong- willed top executive who either does all the buying or who hires a curator to do it. Even so, corporate art hews to the conventional, avoiding anything that is overtly erotic, political, religious, or violent. Most collections consist of contemporary works painted since 1960 because they are plentiful and relatively inexpensive. Although these Medicis claim investment per se is not one of the reasons they buy art, like any other collectors they want to see their good taste validated by the market. But they flat-out refuse to discuss the rising value of their holdings. Fear of theft is one reason, but fear of stockholders may be stronger. Experts consider the art assemblages on these pages to be among the best in the country.

PEPSICO ''We're gonna turn that cow pasture into a new Versailles,'' Donald M. Kendall told a resident of Purchase, New York, who bitterly protested PepsiCo's move to the area in 1970. The Sun King of soft drinks kept his promise. To beautify PepsiCo's sprawling 140-acre suburban headquarters, Kendall, then the chairman, planted exotic gardens and installed 40-odd giant pieces of sculpture by some of the 20th century's best artists. Art critics consider it corporate America's finest sculpture garden; Kendall calls it a museum without walls. A major incentive for an acquisition program is often a new headquarters site. Typically a chief executive will decide to scoop up paintings or sculpture to fill the empty walls, offices, and lawns of the new building. Such was the case at PepsiCo, whose new headquarters was not welcomed by the residents of Purchase, an upper-class, horsy section of Westchester County. Kendall's sculpture collection helped to mollify the community and enhanced the company's reputation for being a good corporate citizen. Kendall, who retired in 1986 but still has an office at PepsiCo, selected and supervised the placement of each piece. Although PepsiCo has never had the collection appraised, Kendall clearly recognized value when he saw it. Between 1970, when he began buying with an eye to the new headquarters, and 1975, he spent $1 million of PepsiCo's money on ten major works; today those ten are valued by a major New York City auction house at a total of $10 million. < If the stockholders think PepsiCo is frittering away corporate assets on art, they never told Kendall. Annual meetings are held at PepsiCo's headquarters, where shareholders can view the latest additions to the collection. Says Kendall: ''We don't even get complaints from Lewis Gilbert.'' Known as a corporate gadfly, Gilbert is a staunch advocate for the rights of small shareholders, and he doesn't hesitate to question management about how it spends corporate funds. One of Kendall's first purchases was Hats Off, Alexander Calder's towering, fire engine red stabile. He spotted the audacious piece at a foundry as he was driving through Connecticut, and fell in love. Holly Solomon, who heads her own gallery in New York City, estimates the Calder could sell today at close to $1 million. Two stylized, lanky figures by Alberto Giacometti, Standing Woman 11 and Standing Woman 111, were also early bloomers in the PepsiCo garden. Martha Baer, head of contemporary art for Christie's, says they are currently worth at least $1 million apiece. For Solomon, the two Giacomettis together assay in the range of $4 million to $5 million. David Smith's elegant Cube Totem Seven and Six is another member of the millionaires' club in Baer's view; she reckons it's worth $1 million. Although small companies have scored in the booming market by selling works from their collections, major corporations rarely part with their purchases. For that reason Kendall doesn't worry about price tags. Says he: ''We're never going to sell anything.''

FIRST BANK SYSTEM INC. ''They get angry about it,'' says Lynn Sowder, the effervescent curator of First Bank System Inc. in Minneapolis, describing employees' reactions to the company's daring collection of modern paintings and sculpture. At every corner of the bank's corporate headquarters, workers are confronted with radical, unsettling art that is atypical of corporate collections. A terrifying canvas by Enzo Cucchi that juxtaposes a long gun barrel with a barren landscape hangs behind a receptionist's desk. Facing that painting is Michael Lucero's giant ceramic head, with a staircase where the brain should be. Just around the corridor looms a disturbing work by Justen Ladda that combines a urinal and a bust of Voltaire, both stamped with the bars of supermarket coding. In 1981 the bank's president, Dennis E. Evans, authorized Sowder to fill the vast walls and atriums of its new headquarters with art that was exciting and provocative. Evans wanted the building to reflect the changing dynamics of a banking business in the throes of deregulation. Says Sowder: ''Art is the most powerful visual symbol of this organization's commitment to change, which is why our collection upsets people.'' Though difficult and controversial, the collection has nonetheless appreciated tremendously. Under Sowder's discerning eye, First Bank has spent about $3 million for 2,800 pieces created since 1980 by American and European artists. The assemblage is insured for $6 million. The return on some of Sowder's picks beats anything the bank can offer. She bought a photo collage called Mouth by two British artists who use only their first names, Gilbert and George, for $10,000. It would fetch $35,000 today. Carroll Dunham's neosurrealist The High Frontier cost $10,000 in 1985, before Dunham became a hot-selling artist. Now the piece is worth about $30,000. What really makes the bank's collection valuable, Sowder believes, is that it helps employees to accept new ideas. She fosters this process with frequent seminars and careful labeling of each piece. And her work has done a lot to win over the employees. A recent survey reveals that only 40% of the bank's employees dislike her choices; last year 69% objected to them. That's just fine with Sowder and Evans. They cringe at the thought of creating the ''wallpaper effect,'' produced by what Sowder calls ''safe and unchallenging'' corporate collections.

STERLING REGAL ''You can't find more beautiful paintings,'' boasts Haig Tashjian, chairman of Sterling Regal, a privately held graphic arts company, as he gazes at the dazzling women who fill his New York office. To be sure, Sterling's collection of oils by American-born realists and impressionists is mesmerizing. Portraits of sensual, high-born young women cover nearly every inch of wall space from the waiting area to the executive suites. Suspended behind the receptionist's desk is Frederick Frieseke's Necklaces (center, at right), flanked by two Matisse-inspired portraits by Karl Anderson. On the opposite wall is Max Bohm's Lucy, an imposing young woman in a winter frock. ''Why should we spend $4 million for a Renoir or $8 million for a Monet?'' asks Tashjian, referring to the exorbitant sums that French impressionist works command. ''I can get a great piece by an American impressionist for under $200,000.'' Tashjian works closely with his curator, Lois Wagner, who about ten years ago firmly focused Sterling Regal's collection on quality landscapes and figurative paintings of women. Says Wagner: ''I've always been interested in representation rather than abstract paintings, and there seemed to be more attractive pictures of women. Besides, Mr. Tashjian adores them.'' The major portion of the collection consists of 180 works and cost the company about $2 million. But the upswing in prices for outstanding examples of American realism and impressionism has been so dramatic that these pieces are now worth $4.5 million. Sterling Regal got in early. In 1978 the company bought Portrait of the Artist's Daughter by William Merritt Chase for $40,000. It is now valued at $400,000, according to New York dealer Robert Preato, a specialist in turn-of- the-century American art. In 1982 Wagner laid out $50,000 for Childe Hassam's delicate Young Girl Reading -- Spring (bottom left); it would fetch at least $150,000 now. One night three years ago Wagner and Tashjian paid $200,000 at a gallery opening for a group of five works, including Souvenirs, a moody portrait of a woman gazing at her keepsakes, painted by Irving Ramsey Wiles. All the acquisitions from that spree have appreciated at least 30%, says Preato. Adds Tashjian: ''It's gratifying to discover that after 25 years of collecting American representational paintings, the art world has finally caught up with those of us who kept the faith.''

BLOUNT INC. One day Postmaster General Winton M. Blount toured a Detroit post office where paintings by employees were on display. For the first time it occurred to him that art could be used to spruce up the workplace and enhance the quality of corporate life. In 1973, when he resumed the chairmanship of Blount Inc., the Montgomery, Alabama, construction company he founded, Blount began to amass some of the best examples of American painting from pre-Revolutionary days to the present. The Bicentennial was on the horizon, and he thought an art collection would be one way for Blount Inc. to commemorate the 200th birthday of the Declaration of Independence. Blount does all the buying for the collection himself; he has hung works he is considering acquiring in the main lobby of his headquarters so employees can weigh in with their opinions. The final decision, however, is based on what he likes. ''Blount has always had a great eye, and he goes after the best,'' notes New York art dealer Lawrence A. Fleischman, a major supplier to the collection. ''He doesn't just want a signature, he wants a major example.'' And he gets it. The company's 100 blue-chip pieces, bought since 1973 for a total of about $5 million, are conservatively appraised at $10 million. The most valuable work is Edward Hopper's quiet but intense New York Office, which Fleishman reckons has appreciated some 900% since Blount picked it up in 1976 for $250,000. Because he is willing to spend what it costs to acquire major works, Blount is not a typical corporate collector who buys emerging young artists in the hope they will turn out to be the superstars of the near future. Among the collection's other jewels are Mary Cassatt's delicate Young Mother in a Floppy Hat . . . , an impressionist piece now worth more than $1 million, and John Singer Sargent's lush portrait of Mrs. Louis E. Raphael. Blount bought it four years ago for $425,000, and last year a comparable Sargent, Mrs. Cecil Wade, brought a robust $1.5 million at auction. In 1977 Blount came by Frederick Church's American Landscape, which shares a wall with the Sargent (above right), for $85,000; its value has risen 300%. Summer Twilight, a high-spirited work painted in 1932 by Stuart Davis, one of America's first abstract artists, has appreciated 900% since Blount acquired it in 1974 and is also worth more than $1 million. Says Blount: ''I think I've made some pretty darn good choices.''

DOMINO'S PIZZA Home in Ann Arbor on leave from the Marines in 1958, Thomas S. Monaghan tried to break the ice with a blind date by chatting about his obsession with Frank Lloyd Wright. The girl replied that she lived in a house designed by his hero. Monaghan promptly drove her home to nearby Plymouth, where she sat for the evening while he inspected every inch of her house. Not surprisingly, Monaghan lost contact with the girl over the years, but not with her house. His privately owned company, Domino's Pizza, bought Snowflake, the Wright dwelling that stands next door. It was Monaghan's first purchase when he took off on a shopping spree in 1984 that is still going full blast. In two years his company has gathered the largest collection of Frank Lloyd Wright objects in the world (some shown above), and Monaghan is on the prowl for more. Since he always pays top dollar, he drives the market, and one of his purchases made headlines last December. He established the record price for a 20th-century chair by paying $198,000 for a high-backed oak dining chair that Wright designed in 1901. Monaghan, who is building a museum in Ann Arbor to house his Wright stuff, has so far spent about $7.5 million on his passion. The collection is appraised at $12 million. Domino's flamboyant chairman has almost single-handedly revived the market for Wright's work. ''When I wrote my book on Wright in 1979, his furnishings were being destroyed,'' notes consultant David A. Hanks. Last year Monaghan bought one of the windows from the Coonley Playhouse in Riverside, Illinois, for about $100,000; now the window is worth $200,000. Wright's color drawings for the 1927 covers of Liberty magazine have doubled since Monaghan laid hands on them in March 1986 for $15,000. Hanks predicts that most objects in the collection will appreciate a minimum of fourfold in five years. Unfortunately, Monaghan is so well known as a Wright-winger that he believes he is an easy mark for what he naively calls the ''old ugly head of greed.'' The owner of Wright's customized 1948 Lincoln saw him coming and bargained him up to $45,000 for the car before Monaghan's curator sent a friend the Lincoln owner wouldn't recognize to buy the car for $31,000. But the friend then demanded $250,000 to resell the auto to Monaghan. Says the disillusioned collector: ''It's amazing how often people do that when they think they have a chance to get into my pockets.''

READER'S DIGEST Reader's Digest, the magazine of Middle America, owns what is indisputably the corporate world's most valuable French impressionist and postimpressionist art. The collection was assembled by Lila Acheson Wallace, co-founder of the Digest, donor of the Lila Acheson Wallace wing at the Metropolitan Museum of Art and consummate connoisseur. When the company's red-brick, Georgian-style headquarters was completed nearly half a century ago, Mrs. Wallace took on the project of decorating it. She had her own ideas about an ideal working environment for her employees, and she turned the ''office'' into an elegant, comfortable home, filling the entire place -- not just the executive quarters -- with expensive antique furniture, sumptuous draperies and upholstery, and fine Oriental rugs. These were the background for her real passions: exotic flowers and beautiful art. The scent of fresh-cut blooms filled the building, and paintings by the great French masters from Bonnard to Renoir adorned the walls. The Pleasantville, New York, headquarters looks the same today as it did in the mid-1960s, when Mrs. Wallace completed her acquisition program. Vases of splashy flowers brighten the rooms, the original furniture is still in place, and the well-known French impressionist paintings are hanging on the walls. There has been one big change, however, but it is invisible. The 50 or so masterpieces are enormously more valuable today than they were when Mrs. Wallace had them installed. In 1951, when Reader's Digest acquired Thatched Roofs at Auvers, a somber landscape that Vincent van Gogh painted a month before his suicide in 1890, it probably cost Wallace about $20,000. David Nash, senior vice president of Sotheby's, reports that comparable van Goghs were selling for that at the time. Nash reckons the Reader's Digest van Gogh would be worth $1 million today. Another van Gogh, Flowers in a Vase, also painted during the artist's last days at Auvers, is thought to have cost Mrs. Wallace about $200,000 when she bought it in 1963. Now Nash estimates that the picture could fetch as much as $3 million. The value of Water Lilies, a huge and vibrant work painted during Claude Monet's final years, has also increased, but more dramatically. In 1961, when Mrs. Wallace bought it, similar Monets were selling in the neighborhood of $25,000, and Nash thinks the painting is worth $2.5 million now. The company's other works have appreciated nicely too. The best performers are probably two elongated portraits that Modigliani painted of his mistress, which came into the collection in 1965. Nash estimates that each portrait cost less than $100,000; today a comparable Modigliani is worth about $3 million. Although the impact of the art on Reader's Digest employees has never been measured, they are particularly attached to it since it has been a major part of their corporate culture for so many years. Clearly the pictures build morale. Employees volunteer to conduct tours, call to report when spotlights are out, and get angry when their favorites are out on loan. When curator Frances N. Chaves was recently crating a painting to send on tour, she was stopped by an irate employee who snapped, ''Where are you taking my Monet?''