Donnnng. Donnnng. The solemn carillon of AC/DC's "Hells Bells" rings out over the loudspeakers in Hong Kong's Conrad Hotel when Tony Shaw — bullish HSBC trader turned raging bull — steps into the ring in a bright-green and yellow robe. In the other corner, Mergermarket's Will Marsden boxes the air as the 500 financial heavyweights crowded around the ring in black tie erupt in a Fight Club frenzy. At last the combatants square off, the starting bell rings, and Marsden launches a wild right hook, misses, and stumbles into the ropes. Seizing the moment, Shaw unfurls a savage one-two combo to the face and Marsden crumbles to the ground, his nose already covered in blood.

Behold Hedge Fund Fight Nite, a white-collar thug-a-thon to benefit the children's charity Operation Smile. Banking and boxing are blood sports both, so it was really only a matter of time until they merged, spectacularly, for what Don King, waving two mini American flags in a pretaped video, calls "The Ding Dong in Hong Kong." Every blue-chip bank — Goldman Sachs, JP Morgan, Merrill Lynch, Deutsche Bank, HSBC, Citigroup — has bought an $8,000 table, if not three or four, and the crowd seems to be unleashing that manic boys'-club testosterone of 1980s Wall Street boardrooms. "What's all this touchy-feely?!" yells a guest during the only marginally tamer brawl between 44-year-old Greg "Bulldog" Jacobson of Countrywide Financial and 28-year-old Mark "Celtic Warrior" Finnie of Mergermarket. "He's twice your age, Finnie, ya big girl!" (Some nicknames turn out to be ill-chosen: The Celtic Warrior is not blessed with the luck of the Irish, handily losing to his elder, and Merrill Lynch's Graham "Slappin" Lappin gets slapped around so severely by Ron "The Anesthetist" Rutland of Fortis Bank that the match is called early.)

The format is simple enough: Six showdowns, each with three two-minute rounds, and in the absence of a TKO, a panel of judges from the Hong Kong Police Force's boxing team decides a winner. The event began in Britain in 2004, though the initial perception was that it was just a bunch of harmless vanilla gorillas. "The first time we did this in London, there was a lot of skepticism," admits Fight Nite founder Adrian Fairbourn, a partner at the U.K. boutique corporate advisory firm Exception Capital. "Then there was a knockout in Round One, and people were like, 'Whoa.'" Each Fight Nite features a new cast of brawlers, and for the Hong Kong adaptation, 28 prospects were winnowed down to a dirty dozen — all expats who live and work in Hong Kong — who, on top of their grueling day jobs, then trained for five months with ex-martial arts champ Andrew Wong Kee at his studio in the financial district. "The first two months were just conditioning," Wong Kee tells me. "Explosive athletic training: Deep squats, chin-ups, heavy weights. Then, in the third month, they put on the gloves and got technical." The potential for bodily harm is so real, in fact, that a team of medics is on hand, and when organizers recently tried bringing the event to New York, they couldn't get legal clearance — hence the relocation to international waters. (In May, yet another Fight Nite — the fifth in three years — will be staged in London.)