The World's Fastest Man wears bright red and yellow track shoes with his nickname--"Mo"--imprinted on the heel. The license plate on his Mercedes reads "Mo Gold." And, as he prepares for his quest to win three gold medals here at the world outdoor track and field championships, he has taken to referring to himself as The Pheno-Mo-non.

It took U.S. sprinter Maurice Greene precisely 9.79 seconds last June to earn the right to such braggadocio. When he topped Canadian Donovan Bailey's world record of 9.84 seconds in the 100 meters at a race in Athens, Greene wasn't content merely to assume his place on track's most prestigious mantle. No, Greene was going to have a little fun.

After all, for the 25-year-old native of Kansas City, Kan., being the world's best sprinter was a terrific job. The faster he finished, the more he got paid. It was a welcome arrangement for someone who, at various times, sold tickets at a movie-theater box office, flipped burgers at a fast-food restaurant, walked dogs at a greyhound track and unloaded boxes at a hardware store.

"That just made me a stronger person," said Greene, who now receives appearance fees in excess of $50,000 per meet and has become a major spokesman for Nike. "You have to put everything in perspective. When you reach one goal, you set another."

Greene, the defending world champion in the 100 meters, eased through Saturday's qualifying rounds to advance to Sunday's 100-meter semifinals, with the final Sunday night. Missing are his major rivals: Bailey, who has been bothered by a nagging Achilles' tendon injury, and training partner Ato Boldon, the defending 200-meter world champion who isn't competing because of a thigh injury. Given their absences--and Greene's own high standards--he would consider a gold medal in the 100 merely a small start to a big week.

A Mo-mentous week, as he would put it, also would include gold medals in the 200 and the 4x100 relay.

"Right now, the most important thing to me is to come out here and win three gold medals," Greene said with a grin after cruising through the first of two qualifying heats Saturday (he won both). "I feel I have to give a little bit more because the show [he and Boldon] we were going to put on is not going to happen now. I want to give a little bit more so, hopefully, the fans will be pleased."

Greene, his grin intact, made the rounds to 12 or 13 clusters of reporters this morning, accommodating television announcers, radio hosts and newspaper writers who lined up to speak with him. Though many athletes hustled through the designated interview area, Greene greeted all comers with a genuine smile and, in some cases, even friendly handshakes.

John Smith, a 1972 Olympian in the 400 who has been Greene's coach since 1996, chuckles at the spirit routinely displayed by his most successful pupil, whether in winning gold medals or, more surprisingly, in getting a sleepy group of sprinters to wake up for early Monday training sessions. Greene trains with Boldon, Jon Drummond and other members of Smith's training group, Hudson Smith International (also known as "Handling Speed Intelligently") in Granada Hills, Calif.

"On Monday morning, he will say to everybody: 'Thank God we're not at a desk! We're out here doing what we love to do! Everybody have a great week!' " Smith said. "He shouts this out at practice."

Greene shrugged off his customary motivational speeches.

"We have a group that's so together, we all help and complement each other," he said. "Our goal, whenever someone is starting to slack off, or doesn't want to go to practice, is to help each other to achieve our goals."

USA Track and Field publicity manager Tom Surber has dealt with plenty of athletes who have a lesser appreciation for the value of marketing themselves. Surber said he was pleasantly surprised at the enthusiasm Greene and Drummond displayed at a children's track clinic in Eugene, Ore., in June--one day before the start of the national championships.

A 6-year-old boy insisted he could beat Greene in a race. Greene grimaced as if angry and challenged the boy to a sprint. Drummond acted as the starter, and after signaling the start, tackled Greene. Once Greene got off the ground, he couldn't seem to muster his usual speed. The 6-year-old defeated Greene handily, and received a victory ride on the shoulders of Drummond. "They had more fun than the kids," Surber said. "And the kids had a ball."

"We appreciate his bringing the record back to the United States," said USA Track and Field Chief Executive Officer Craig Masback, who has emphasized public relations since taking over the association two years ago. "And Maurice, as a bonus, is naturally friendly, approachable--the kind of person who enjoys the role of being the world's fastest human. His joy--and enjoyment of his status--is refreshing."

There was a time when there didn't seem to be much for Greene to enjoy. He did not excel at his studies as much as he excelled at running, and he attended junior college after high school, following in the footsteps of his brother Ernest, a national junior college champion in the 200 meters.

Greene watched the 1996 Olympics on television after failing to make the U.S. team. (He finished seventh in the quarterfinals at the Olympic Trials in 1995.) He was trying to figure out which odd job he would try next when he got in touch with Smith, who had followed Greene's progress since Greene's days at Schlagle High School in Kansas City.

Though Greene was reluctant to leave his high school mentor, Al Hobson, he decided to join Smith's group after his disappointment at the Trials.

"He called me up and said, 'I'm in town, when's practice?' " Smith said. "I said, 'Let me ask you a couple of questions: How good do you want to be?' He said, 'I want to be the best. I want to bring sprinting back to America and be the best that ever was.' "

Smith figured a kid with ambitions that large needed an equally grand introduction to the demanding world of elite-level track and field. Greene was so overwhelmed by Smith's workouts, he cried during some sessions, standing in the track infield to hide his tears.

Smith saw the tears, but he wasn't concerned--as long as Greene continued to show up.

"If he quit," Smith said, "that meant he wasn't the one."

Greene's career reversed course in the summer of 1997. He upset Boldon and Bailey at the world championships in Athens and finished the year ranked second in the world in the 100 by Track and Field News.

Early this year, Greene set his sights on winning three gold medals at these championships. He worked out during the spring with the 1,500-meter runners in the HSI group, determined to build his strength.

"I always set standards high," Greene said. "Someone might expect a lot out of me, but I believe I expect 10 times more than the average person expects.

"[Smith] says anyone can run fast, but it's how you run fast. You have to go into everything with a plan. That's why I've come out here to win three gold medals."