Frisbee, in case you hadn't noticed, can be more than a diversion.

A growing number of people no longer are content simply to throw the plastic flying saucers back and forth. No, these people are not truly happy unless they are, say, throwing a Frisbee 300 or 400 feet, catching one behind their ears, spinning one on their fingers, juggling one off their knees and elbows, rolling one down their arms, performing all sorts of miraculous routines, as well as the most remarkable pitches and catches.

Frisbee has become quite competitive. The world championships are held in the Rose Bowl, no less. There's a game called "Guts Frisbee," in which members of one team try to throw the disc so hard members of the other team can't catch it; Frisbees can go 90 m.p.h. and yu can break your finger, maybe worse. There's even a game called "Ultimate Frisbee." There's competition for very young people, older people, and dogs.

Many of the masters of Frisbee, including a Labrador retriever, gathered yesterday in the Mall to celebrate the Smithsonian's first annual Frisbee Festival, a pleasant addition to the Smithsonian's kite and boomerang festivals. Several hundred people, many with Frisbee, showed up to see the experts give demonstration and worekshops.

The idea wasn't to turn everyone into the next Peter Bloeme - he's the 1976 overall world Frisbee champion. You could learn, for example, how to improve your Frisbee catch so as to reduce the bending over to pick up one you missed.Or one could just watch a Frisbee in unpredictable flight, not an unreasonable way to pass a Sunday afternoon.

But the experts say once you pick up a Frisbee the most difficult move is putting it down; you can quickly become an expert. Michael Collins, director of the National Air and Space Museum, host of the event, looked as if he might be more at home in space at the beginning of the day when he first started throwing Frisbees, but before long he was trying to keep pace, and with some success, with Kerry Kollmar.

Kollmar, 23, 1975, champion, learned his Frisbee in New York's Central Park, then added new dimensions to the game. Quite by accident, while missing catches, he says, he invented the "nail delay" and the "air brush." In the "nail (as in finger-nail) delay," you catch and spin the Frisbee on your finger. "Air brushing" means brushing or batting the Frisbee with the inside of your hand, one purpose being to move the disc upfield in the "Ultimate" game.

("Ultimate Frisbee" resembles non-contract football. It's played by two seven-person teams and a goal is scored when a player passes the Frisbee to a teammate in the end zone.)

Dave Johnson, known as "Mr. Distance" because he once threw a Frisbee 412 feet (on a windy day in Boston), made a throw of 332 feet, judged herculean given the "heavy" Washington air. His throws pleased the crowed almost as much as Martha Faye's catches.

Martha is the dog, her master being John Pickerill, of Fredericksburg, Va. Martha leaps up to 6 feet and snaps the Frisbee out of the air."One of the best free-styling dogs in the world," said Larry Schindel, founder of the Washington Area Frisbee Club and chairman of the Ultimate Frisbee Players Committee. (Schindel is from Maplewood, N.J., birthplaceeee of the "Ultimate game.)

As Martha was warming up for some length-of-the-field catches, Goldie Norton, a representative of Wham-O, the company that manufactures the Frisbee, mentioned a West Coast whippet named Ashley Whippet, who is said to leap almost everthing short of tall buildings to snare Frisbees.

MTA's and TRC's also were demonstrated - that's maximum time aloft and throw, run, and catch. Jack Roddick, the seniors champion (he's 56) from Shippendsburg, Pa., said that Frisbee golf courses, springing up around the country, appealed to him because "people my age, we don't groove on the running and catching."

There seems to be something for everybody in Frisbee, and who would have thought that back at the Frisbee Baking Co. of Bridgeport, Conn., where it all began shortly after World War II. People sailed the empty pie tins back and forth, and before long the game took off. Now there are more than 80,000 members of the International Frisbee Association, and, as of yesterday, Frisbee has gained a place in history. That occured when Schindel presented to Collins a special Frisbee for showing at a future Air and Space Museum exhibit.