(FORTUNE Small Business) – Shortly after taking over the struggling National Lacrosse League three years ago, Jim Jennings drove to Philadelphia to watch what would be only the second live Lacrosse game of his life. He took a seat in the First Union Center, home of the Sixers and Flyers, and scanned the crowd. He'll never forget what he saw: men who looked fresh from a barstool; families wearing Philadelphia Eagles jerseys and cheering wildly for the hometown Wings; little boys with long hair. "They didn't look like the preppy types that have traditionally played and watched Lacrosse," says Jennings.

The commissioner quickly ordered a survey. The results confirmed his hunch --80% of the fans said the Wings were their first bite of Lacrosse. The preppies in the Main Line suburbs, preferring the collegiate outdoor game, turned up their noses at the indoor pros. But raucous Philly sports fans, with their passion for hard checks and high scoring, loved them. "When I go to games, I'm the only guy in a suit in the whole arena," says the boyish 42-year-old Commish, a former college wrestler.

He devised a paradoxical plan--move the NLL, which debuted in 1987, out of the sport's Northeastern hotbeds. Teams in Lacrosse-mad areas like Baltimore and Washington, D.C., and on Long Island, N.Y., struggled because fans there grew up on outdoor Lacrosse. So Jennings looked west, moving the New Jersey Storm to Anaheim, the Albany Attack to San Jose, the Columbus Landsharks to Phoenix, and the Washington Power to Denver. (The Baltimore Thunder moved to Pittsburgh in 1999, and the Long Island team, the New York Saints, folded last year.)

The westward expansion has paid off for the ten-team NLL: Jennings has increased revenues 400% over the past three years, to $21.4 million in 2003, and the league turned a profit, of $250,000, for the first time in 2002 (the league projects a similar profit for 2003). Average attendance jumped 11%, to 8,658 a game last season, and starting this season, which began in late December and runs through April, Fox Sport Net's regional cable networks will pipe games into 55 million homes, complementing the league's deal with Canada's Score network. (Three-fourths of the NLL's players come from Canada, where indoor, or "box," Lacrosse is a major youth sport; Calgary, Toronto, and Vancouver are NLL cities.) Since Jennings took over, the entry fee for a new franchise is $3 million, up from $500,000 in 2000.

Much of the credit for this momentum goes to Jennings. Although he has received an assist from Lacrosse's recent emergence as one of the fastest-growing youth sports in the U.S., Jennings has had to fight for his place in a saturated sports landscape, where countless upstart fringe leagues have disappeared. Most recently women's pro soccer (WUSA), started in the surge that followed America's 1999 World Cup victory, collapsed last September. "The fact that Lacrosse has survived, much less grown, is a major accomplishment," says Chicago-based sports-marketing consultant Marc Ganis.

But Jennings, like most entrepreneurs, has higher goals than mere survival. "No doubt he's capable of running a major sports league one day," says Golden State Warriors head coach Eric Musselman, who worked with Jennings in the minor-league basketball circuit. Jennings, however, thinks that that major sports league is the NLL: "I want to get us up to 29 teams within the next seven years and become the next NBA or NHL," he says. That's an ambitious goal in the best of times, but considering Jennings's history of turning barnstorming franchises into valuable properties, he's earned a shot.

If Jennings is going to make indoor Lacrosse a bigtime sport, he's going to have to reach out to those kids in the emerging talent pools of Lacrosse players in the Deep South and the West. He revived the sport's Scoop n' Shoot competition (similar to football's Punt, Pass & Kick program, whose alumni include John Elway and Brett Favre), after Lacrosse's governing body, U.S. Lacrosse, let it fall dormant. Before a game in each NLL city, boys and girls hurl a half-dozen balls at the goal. Those kids--last year 700 of them between the ages of 9 and 14--are paying customers, along with their parents, at about $25 a pop.

Jennings has also made a deal with Nickelodeon to promote the contest on its gaming and sports channel, Nick GAS (which is available on cable in 18 million homes). The network ran 1,000 Scoop n' Shoot commercials last year and will do the same in 2004. "More kids know they can play indoor now because of Scoop n' Shoot," Jennings notes. "The TV exposure has had a clear trickle-down effect."

Beyond upping the kid appeal, Jennings's biggest challenge has been to solidify the ownership of the league's teams. "Over the years you hear the stories of missed paychecks," says Jake Bergey, 29, a seven-year veteran of the Philadelphia Wings (whose day job is co-owner of a Mexican restaurant in West Chester, Pa.). "I am glad to see the league weed out the bad owners." Jennings has done so by exploiting the natural similarities between box Lacrosse and hockey. Both offer six-on-six play within a glass-enclosed rink, plenty of body checks, and roots in the wilds of Canada. So he reached out to National Hockey League owners in the cities that, despite scant exposure to hockey, embraced the sport during the NHL's expansion and relocation period of the 1990s. NHL owners in Anaheim, Denver, and San Jose (and older teams in Philly and Buffalo) have invested, making offers to previous owners that they couldn't refuse.

Jennings's sales pitch is simple: Lacrosse draws not just bodies but passionate fans. Two summers ago he sat in a conference room with nine members of Silicon Valley Sports & Entertainment, the entity that runs the San Jose Sharks. He popped in a video of an NLL game and asked the group to notice all the painted faces. "Seeing the big crowds and hearing all the cheering, you could just tell that the game had appeal," says Malcolm Bordelon, 45, executive vice president of the SVSE. "The video got us interested, and Jennings struck me as a bright young guy who can deliver on his promises."

This partnership with an established league helps both the NLL and its new owners. The hockey teams can fill their arenas, at low cost, for eight extra nights a season. Teams don't need to add staff--the NHL front office staff can sell tickets and popcorn, shaving six figures off the budget. (Each team's largest expense is player salaries, but the annual average is just $12,000; each team carries 23 players for the 16-game season.) And most important, the NLL gets owners with experience. "These people know what makes their cities tick--they know marketing, public relations, advertising," Jennings says. "A partnership makes more sense than trying to reinvent the wheel."

The Colorado Mammoth is the league's star pupil. During its first season in Denver last year, the Mammoth averaged 16,500 fans a game in the 18,000-seat Pepsi Center and took in nearly $3 million in ticketing and local sponsorship revenues, tops in the league. To spark interest in pro Lacrosse before the NLL season, the Pepsi Center hosted a Mammoth exhibition game 45 minutes after a sold-out Avalanche hockey contest. About 9,000 people stuck around. The players also gave clinics at some 100 area schools. Plus, Mammoth games have literally become a party. After each game players from both teams head to the Pepsi Center's Blue Sky Grill to hang out with fans and sign autographs.

Other teams have followed suit: The San Jose Stealth, which starts play this season, hosted an exhibition after a Sharks game in November and drew 11,000 people. San Jose has sold 2,500 season tickets in its first four months; last year in Albany the same franchise sold 400 all year.

More than any savvy business deal or creative promotion, Jennings's background is what makes him unique among sports commissioners. He didn't parachute in from a fancy law firm but rather grew up in the minors. At 21, he took his first job out of college selling tickets for the New York Cosmos of the North American Soccer League. The Cosmos folded in 1985, but Jennings, who after two years pushing tickets became marketing director, learned a crucial lesson: The sport alone doesn't sell; you have to entertain the fans. Rod Stewart played halftime shows, and young, caffeinated kids jostled over autographed carrots that Bugs Bunny hurled into Giants Stadium seats. (Warner Communications--now part of Time Warner, parent of FSB's publisher--owned the team.) "We used to say we were throwing rock concerts," says Jennings, "and a soccer game happened to break out."

An off-season job parking cars at a Jersey-shore restaurant turned into a full time gig after the Cosmos folded, and in 1992, Jennings sold the 325 franchises of his company, Valet Park International, for $4 million. Looking to relax for a year, Jennings moved to Florida. While in Sarasota he met Musselman, then coach and general manager of two minor-league expansion basketball teams. Musselman asked Jennings to operate the franchises while he focused on drawing up plays.

Jennings quickly became the Mark Cuban of minor-league hoops, without the whining and fines. Instead of seeking cash from a local hotel for arena ads, he secured free rooms for his players. He traded ads for Burger King meal vouchers so that his guys could eat on the road. "In minor-league basketball, that's being treated like royalty," says Musselman. Word spread, and the best players flocked to Florida; his teams played in four championship series in four years, winning twice.

Jennings returned north to buy his own minor-league teams. He put $50,000 into the USBL's New Jersey Shore Cats in 1997 and bought the Pennsylvania Valley Dawgs for the same price in 1998. He attracted buzz to the attention-starved summer-league teams by hiring former NBA stars Rick Barry and Darryl Dawkins to coach. Jennings sold the franchises in 2000 for $800,000 apiece.

Having earned a reputation as a builder, Jennings was recruited by the NLL owners in 2000. "Based on what I did with these teams, I knew I was a good fit for the Lacrosse job," Jennings says. "We were getting 5,000 fans a night, yet I was selling these teams for $800,000. I saw how undervalued the Lacrosse teams were." He's already accomplished two of his goals--the westward move and a rise in franchise values. The third, becoming a 29-team league that rises to be the fifth major American sport, seems a little far-fetched, even dangerous. "The biggest mistake secondary leagues make is that they grow too fast, spreading on-field talent and financial resources too thin," says marketing consultant Ganis. "This plan will send the league on the steep slide to oblivion."

Jennings, for his part, isn't listening, because he's been there. "Our game has it all--it's fast, it's hard-hitting, and it's once a week, like football," he says. "I have good reason to be real ambitious."