Tony Hawk's skill on a skateboard can be measured in degrees—720 degrees, to be precise. That's two complete midair somersaults, and Hawk, 18, is the only person in the known world who can execute them on a 31" hunk of laminated maple with wheels. To the abiding amazement of the regular crowd at the Del Mar (Calif.) Skate Ranch, where he practices almost every day, he hurtles his gangly 6'1" frame off the curving wall of the concrete bowl, tucks into his patented double flip, and then knifes out in time to land effortlessly on the pavement about where he left it. Says one of the regulars, reverently, "He can do anything on a board."

Not quite. Hawk's goal is 2½ complete turns, which he's failed to make. But many of the twists, flips and handstands that Hawk has perfected are so original he has to name them as he goes along. "Sometimes I can't wait to skate," says the inventor of the Madonna, the Varial and the Frigidaire, "because I don't know what new tricks I'll come up with that day."

Hawk's long legs often display nicks and dings from his experiments, which have also cost him big chunks of his two front teeth (they're capped) and a few concussions, but his board, with a spray of ads across the bottom, bears witness to his success. Skateboarding isn't a casual after-school diversion anymore. In four years it has shot from a $4 million hobby to a $300 million industry, and skatemaster Hawk, a recent graduate of Torrey Pines High School, is its highest-paid professional. Last year he earned more than $100,000—some $10,000 in prize money generously compounded by stunt work and endorsements. He has appeared in Police Academy IV. He's done commercials for Mountain Dew and Matchbox Toys. He has five corporate sponsors, including: Powell-Peralta, the skateboard manufacturer, which recruited him to its pro team (the Bones Brigade) when he was 14 and is marketing a line of boards under his name; a Stubbies line of Tony Hawk shirts and shorts; and Swatch, which asks only that Tony wear two of its watches, which he does, whenever he appears in public. "I have a lot of sources of income," he says.

Last year Hawk bought his own four-bedroom duplex in Carlsbad, a mile from his parents' home. (Thanks to his son's success, Frank Hawk, an importer, also is a founder and current president of the National Skateboard Association.) Tony shares his new quarters, which feature a backyard Jacuzzi and lots of stereo and video equipment, with three rent-paying skateboarders. When he isn't performing in places like Sweden, Italy and Japan, he is apt to be at the Skate Ranch. "I have to keep progressing, doing something I haven't done before," says Hawk. Doesn't this stuff frighten him? "It's exciting to be upside down in the air and have the feeling I know where I'm at," he says. "But," he concedes, just a little reluctantly, "the new tricks are still scary."