The Cherry Blossom Classic this morning promises to be one of the largest participatory sports events ever held in the Nation's Capital.

A massive field of 2,230 distance runners, rivaling the draw of the Boston Marathon, has entered the 10-mile road race scheduled to begin at 9 a.m. near the golf clubhouse in East Potomac Park. Five minutes later, several hundred additional runners will begin a two-mile "fun run" in connection with the classic.

The races comprise the second-largest distance-running event in the U.S. Only the Bay-to-Breakers race in San Francisco, which last year attracted 9,000 participants, is larger.

The field for the 10-mile could have been bigger, but the D.C. Road Runners Club, which has conducted the classic since 1973, turned down more than 500 later applications, including some from top-ranked runners, in the interest of safety.

At the sound of the starter's pistol, the 10-mile competitors will head around Hains Point and up to the Potomac River side to the Tidal Basin.They will circle the Tidal Basin once, make a short out-and-back sally along the river toward the Lincoln Memorial, then retrace the Hains point route back to the starting line.

Best vantage points for watching the race are the Jefferson Memorial and portions of West Potomac Park. East Potomac Park will be closed to auto traffic after 8:45 a.m.

Runners to watch include Carl Hatfield of the West Virginia Track Club, defending champion and course record-holder in 49:09; Sam Bair of Pittsburgh, the 1973 winner, and local favorites Max White, Phil Stewart and Bruce Robinson of the Washington Running Club.

The favorite in the field of 230 women runners is Julie Shea, 17, of Raleigh, N. C., who set a U.S. record in winning the female division last year in 57:04. She is likely to be challenged by her sister, Mary, and by Aileen O'Connor, local CYO runner who recently won a national junior cross-country championship.

Following the leaders will be a diverse pack of runners representing 25 states and Canada. Entrants range in age from Victor Grossman, 74, a retired Silver Spring postal worker, to Jennifer Amyx, 7, who ran an Olympic-length marathon at five.

By occupation, the field includes 25 policeman and two firefighters, 30 journalists, 40 physicians, 20 economists, 20 physicists, three FBI agents and two Secret Service men, a chaplain, a professional model and a sleep researcher. A 20-member physical education class at the University of Maryland has entered the race for its "final exam."

One noteworthy entrant is Mayor Kenneth Gibson of Newark, N.J., a veteran of three 26-mile marathons.

SPonsors have purchased 2,200 commemorative patches, 400 gallons of Gatorade, and 9,000 safety pins for use in fastening 2,230 competitors' numbers.

The classic, which in five years has grown from a modest 129 finishers to its present size, attracts both national-class racers and novice joggers hoping only to complete the distance. For sesoned runners, the classic is considered an ideal tuneup for the Boston Marathon April 18.