The vicious attack didn't begin to satisfy the crowd. They wanted blood, and Shamrock, who calls himself the world's most dangerous man, had merely given them a broken ankle.

''They were throwing things at me,'' said Shamrock of the Denver audience at the first Ultimate Fighting Championship in 1993. ''They were so mad that I had a hard time getting out of the arena. Can you believe it? I broke his ankle, and they wanted more.''

Now, less has become so much more for mixed martial arts, which combines judo, boxing, karate, Muay Thai, kickboxing, tae kwon do, jiu-jitsu and wrestling.

By restricting the violence, the sport has found its way back into the spotlight, attracting new fans without alienating its original hard-core base.

''The way I look at it, it's a fight, and violence sells,'' said Ron Kort, CEO of New Era Fighting, a new MMA series. ''WWE (World Wrestling Entertainment) is great, but it's fake. UFC is great, because the violence is there. We're trying to add entertainment with violence.''

And business is booming.

The International Fight League has deals in place with Coca Cola's Vault energy drink, Suzuki and Microsoft's Xbox. Meanwhile, the UFC is challenging WWE in pay-per-view profits, and networks are scurrying to line up MMA shows.

The UFC, Japan-based Pride Fighting Championships, King of the Cage and newcomers IFL, Elite Xtreme Combat and New Era Fighting, to name a few, have turned MMA into a big-money venture.

UFC president Dana White, who, with the help of brothers Frank and Lorenzo Fertitta, took over and revitalized the struggling company in 2001, welcomes the competition. But he worries a serious injury in any series will damage the sport's carefully refurbished image — one he has spent years and millions of dollars crafting.

''Anyone who can rub two nickels together to buy a cage, and can combine three letters together, is coming into the sport,'' White said. ''But the bad guys and shady companies can end up hurting it. I'm always worried that something bad is going to happen. And it will reflect bad on us.''

MMA has been approved in 22 states, with several more introducing legislation to sanction it. Still, there are several states that have yet to accept the sport — including New York.

It's up to Marc Ratner, the UFC's vice president of government and regulatory affairs, to dispel old myths.

''Some still think it's 1993 when it was no holds barred and anything goes,'' Ratner said.

That he contends was the old UFC, where two combatants entered the Octagon ring and one came out, usually smeared in blood. Back then, there were basically only two rules — no biting or eye-gouging.

''No politics, just two guys fighting,'' said Shamrock, now a coach with IFL.

It was politics that got the sport banned in many states. Outraged by the brutality, Arizona's Republican Sen. John McCain lashed out at the barbarism of MMA, calling it human cockfighting.

Some argue nothing has changed.

''The purveyors of this brand are smart and have positioned it as something other than what it is _ Roman-aged Coliseum matches. ... It's a blood sport. It's as simple as that,'' said Larry Bisig, a member of the Kentucky Sports Authority, a group that works to attract events to the state but doesn't have any regulatory powers.

''It's beyond comprehension that a cock rooster has more protection in Kentucky than does a human.''

Years ago, Ratner, the executive director of the Nevada Athletic Commission for 13 years, agreed. He even appeared with McCain on CNN's Larry King Live to extol the evils of the sport.

Now, he's promoting the UFC and its new wave of fighters.

They include Josh Koscheck, a 2001 NCAA Division I wrestling champion at 174 pounds at Pennsylvania's Edinboro University, who's four credits short of earning his master's degree in secondary counseling. He got bored with wrestling and turned his attention to MMA. Although not as advanced as other competitors in martial arts, he's still feared.

''I have my black belt in wrestling,'' laughed Koscheck, who's 10-1 in MMA events and made his debut in 2005. ''This takes a strong work ethic and discipline. You have to be intelligent.''

That's because an MMA fighter must master ground techniques, judo throws, handwork and footwork for boxing, plus defenses against various forms of martial arts.

''MMA is like chess. You have to think several moves ahead,'' rising UFC star Nate Marquardt said. ''That's going to weed out a lot of non-intelligent people. It's all about training.''

That's Marquardt's specialty. The 27-year-old owns a mixed martial arts gym in Denver with his wife, Tessa, and travels to Albuquerque, N.M., a few times a month to work out with trainer Greg Jackson.

''If you take a good MMA fighter today and put them against the best MMA fighter back then, the fighter today would dominate,'' Marquardt said. ''Today's fighters are just so well-rounded. The technique has gotten better over time.''

As for critics who say it's still too vicious, Marquardt laughed.

''Once you understand the sport, you realize it's not that dangerous,'' he said. ''But there's always people who will say it's rough.''

That's because the sport's bloody past is tough to forget.

Kimo, a former UFC fighter now with New Era, fought Brian Johnston on an independent card in April 1997. Kimo's face smashed into Johnston's head, opening up a wound so deep his cheekbone stuck out. Kimo shielded the 4-inch gash from the referee and won the fight with a forearm choke hold.

''It also hit an artery so the blood was spurting,'' Kimo said. ''If the ref would've saw it, he would've for sure stopped it.''

That's why Ratner helped establish unified rules for the sport in 2000, adding judges, rounds, time limits and weight classes. New Jersey was one of the first states to re-sanction MMA.

The Pennsylvania state athletic commission's five-panel board recently sanctioned MMA after outlawing it in the mid-'90s.

''When I first saw the sport, it was brutal, simply brutal,'' said executive director Gregory Sirb, who's been with the commission for 17 years. ''It was Roman gladiators. We were totally against it. We had to get to a comfort level. The interest level in this is unbelievable.''

There's even fantasy MMA, where participants draft a team like fantasy football. MMAplayground.com, a six-month old Web site, already has close to 10,000 subscribers, said Sam Jacobs, who moderates the site.

''I used to have 20 people over at my house for pay-per-view events,'' Jacobs said. ''I had so many that wanted to come over I had to cut it off because people were stepping all over each other. I know of at least six groups of 20 that have spawned off.''

As the number of fans grow, so, too, do the various MMA series. EliteXC held its first fight Feb. 10 in Southaven, Miss., drawing 7,000 fans. The bout was aired on Showtime. The first five fights of the night also were streamed on the series' Web site, where another 100,000 fans watched.

''It's an exciting time to be in this sport,'' said Douglas DeLuca, CEO of ProElite, which operates EliteXC. ''I look down the road and see this as an Olympic-recognized sport. I see us leading that charge and helping to create a true World Cup system, where truly the best fighters from around the world and different nations compete.''

For now, television is where the competition is at. UFC has parlayed its popularity into a reality show on Spike TV. The season 4 premiere of ''The Ultimate Fighter'' last Aug. 17 drew 739,000 male viewers in the coveted 18-to-34 demographic, according to the Nielsen ratings, crushing Major League Baseball's Detroit-Texas game on ESPN (118,000).

The fifth season begins April 5.

''We've been very happy with the series,'' said Brian Diamond, senior vice president of sports and specials for Spike TV. ''It's been phenomenal.''

MyNetworkTV recently began airing the prime-time show IFL Battleground. The network reported its ratings are up nearly 400 percent in the 18-to-34 demographic from the same time slot last month.

The IFL, which staged its first fight nine months ago, features the first team-based professional MMA league. The 12 squads are located in 10 different U.S. cities, including Seattle, Chicago and Los Angeles, plus Toronto and Tokyo.

News Corporation, Fox's parent company, has invested $6 million in the IFL to become an equity partner, the league's co-founder Gareb Shamus said. And the IFL's trading over the counter as a public company, closing at $9.75 a share Wednesday.

''We've been working at an extraordinary pace,'' said Shamus, who co-founded the league with friend Kurt Otto, now the IFL commissioner.

Pride Fighting also is trying to gain ground in the United States. Pride vice president Sotaro Shinoda said the company is looking to expand beyond its Japanese roots.

''The MMA market is very hot,'' said Shinoda, whose Feb. 24 event in Las Vegas drew nearly 13,000 fans. ''We want to have even more events in the U.S.''

More events, more money. Still, the WWE doesn't consider MMA a threat to its pay-per-view revenues.

The UFC had 10 pay-per view events in 2006 that generated more than $200 million in customer retail revenue, according to an executive familiar with the numbers. WWE said it had 16 events that generated about $200 million in revenue. HBO, through its boxing shows, had 11 events, reporting revenue of $177 million.

''They're a sport, we're sports entertainment,'' said Geof Rochester, WWE's senior vice president of marketing. ''Do I consider them a threat to boxing and boxing's pay per view? Absolutely.''

That's because boxing is struggling to find its next superstar.

''If I went to any high school in the country who has a wrestling team and brought (Ultimate Fighter) Chuck Liddell and (boxer) Floyd Mayweather Jr., everyone would know Chuck and some would know Floyd,'' Ratner said. ''Mixed martial arts has just done a great job.''

Nick O'Neal, vice president of advertising and marketing for King of the Cage, is working on his University of Tennessee master's thesis _ why fans get attached to MMA events and the fighters.

''It's on par with NASCAR,'' O'Neal said. ''People once thought that sport was for hillbillies and car freaks. Now, it's extremely popular. MMA is always going to have that stigmatism of being a bad sport. But as it evolves and becomes more accepted, it's going to become more popular. Personally, I wonder why it's taken this long.''