By Carol Davenport

(FORTUNE Magazine) – DON IENNER, 36 COLUMBIA RECORDS In 1969, after a back injury ruined his dream of playing major league baseball, Ienner began a music career delivering mail at Capitol Records. Today, as the new president of Columbia, which is owned by Sony, he manages the operations of the world's largest record label. Ienner (rhymes with finer) was lured to Columbia from Arista Records, where he helped launch new artists, including Whitney Houston, and reignited the careers of seasoned musicians like Carly Simon. Now he plans to develop the sales potential of Columbia's roster of over 100 musicians, which already includes such chart busters as George Michael and Bruce Springsteen. He'll also look for promising newcomers to carry the company into the 21st century. ''We like hit records,'' says Ienner, ''but we much prefer hit artists with long and developing careers.''

JUDITH H. MONSON, 42 SEAGRAM CO. Monson says she likes to ''take responsibility and run with it.'' Lately, she has been running all over the world as vice president of finance for Seagram's $2.4 billion international division. Besides supervising the budgets of affiliate operations in 28 countries, she evaluates acquisition proposals and helps develop global strategies. Monson, who joined Seagram in 1974 after earning a Harvard MBA, rose from financial analyst to director of corporate development before assuming global powers two years ago. Though she finds business travel exhilarating, Monson has yet to master a foreign tongue. ''I own lots of language books,'' she says, ''but I usually look at them only after I return from a trip.''

DAVID F. D'ALESSANDRO, 38 JOHN HANCOCK MUTUAL LIFE INSURANCE CO. Hancock's former public relations chief is proving he can generate profits as well as publicity. In mid-1987, three years after the Boston insurer hired him to revitalize its corporate image, D'Alessandro was charged with turning around the $1.2 billion group insurance unit. The division, which provides health and life insurance to employees of over 1,000 companies, was $40 million in the red at the time; D'Alessandro restored profitability within a year by cutting 400 people from his payroll and selling money-losing businesses, such as HMOs. He recently became the youngest executive ever elected to Hancock's eight-member management committee.