Half the score in a ride comes from the bull's performance, the other half from the rider. Bulls are judged on speed, force, breaks in rhythm, height of jump and kick, and intensity of spin. The rider is judged on his ability to hang on without flopping around like a ragdoll.

The bull is bareback, with a rope tied around its chest right behind its front legs. The rope is weighted, so that as soon as the rider is off, it slips loose. The rider holds the rope with one hand, and for eight seconds that hand must not lose its grip. The rider's free hand cannot touch the bull at all. Another, smaller rope is tied just in front of the bull's hips. It is not, as the sport's detractors claim, cinched around the testicles. This flank strap is supposed to be loose enough so that a man can slide his hand underneath it. It is there simply so the bull can feel it, because its presence encourages a better kick. (If it's too tight, though, the bull just fidgets.) But the best bulls need no prompting to kick -- just the weight of a man and the gate thrown open.

When you talk to bull handlers, they make the riders seem almost extraneous. Bulls have personal records, and some spectators follow individual bulls as much as riders.

Charges of cruelty are often leveled against bull riding, and for those who find the employment of animals sadistic, there is no getting around it: This is an abrasive and unapologetic sport. There are certainly cases of animal abuse further down the ranks, but at the pro level, no one can afford to hurt a bull. Simply put, they are much too valuable. Between every event, bulls receive a mandatory two-week break; sometimes they're even flown in 747s to cut down on their road time. A good performer is worth upwards of a million dollars. A package of semen from such a bull has gone for $35,000.

At a Sacramento event in January 2009, a young rider was bucked off in 2.9 seconds and reacted by hurling his face-mask at the bull. The 2,000-pound animal seemed hardly to notice, but the rider was roundly denounced from every corner of the profession. He was fined $7,500, forced to make a televised apology, and sent to an anger management class. You don't mess with the bulls.

PBR co-founder Cody Lambert responded to the rider's tantrum by saying, "It's just the thought that he'd be mad at that bull for just doing his job -- that's disgusting to me."

Lambert is a man who understands bulls. He is often seen on horseback in the arena, swinging a lariat to drive or drag out the more stubborn ones. He is the guy who decides which animals get to enter into competition.

"I don't care if they're big, small, mean, nice -- that's just personality," he explains. "They're just like the riders. Some of them are wild, some of them are real friendly, some of them are shy. That doesn't really carry over to their riding. When they are in the arena, they're working."

Like most people on the circuit, Lambert has his heroes. His favorite is Red Wolf, a legendary bull recently retired to pasture and sire after a remarkable seven years on the job. (Most bulls last two or three before retirement.) "He was a great champion," Lambert says. "He never had an off day or a lesser rider. He went up against champions his whole career. Even at the very end, 13 years old, he was a bull they rode and they were going to score 90 on him."

Lambert explains that when Red Wolf bucked off someone in two seconds or less, he simply turned around and trotted out of the arena. But if a rider held on for longer than that, the bull knew it and was furious. He would throw the rider and go after him, and then after the bullfighters, and then he would do laps around the arena hooking everyone else up into the stands.

"Getting on a bull like Red Wolf, you know he's going to do his half of the job, and if you do your part and don't make any mistakes -- and maybe get a little bit lucky -- you're going to win," he says.

There was nothing in Lambert's voice to suggest dominance. He spoke with unexpected reverence, telling me it's simple: A bull has to have ambition to get this far.