The Boston Marathon once again has successfully fought off the growing commercialization of amateur distance running, but not without paying a price.

Because the organizers of the race have refused to pay prize or appearance money, the field for Monday's 89th running of the world's oldest marathon will be one of the weakest in the event's history.

The No. 2 runner in the field, Ron Tabb, withdrew this past week. Tabb, the 1983 runner-up from Eugene, Ore., said he was withdrawing "for business reasons. I'm in good shape and I want to save my stuff for a race that's more rewarding. I know now I'm ready to run a good marathon. I don't want to waste it . . . With Boston, there is no incentive to go out and bust yourself."

"A lot of people think it would damage the race if we gave prize money," said Tom Brown, 71, president of the Boston Athletic Association, the organizer of the 26-mile 385-yard race.

"I don't foresee any change in prize money," said Guy Morse, administrator of the Boston Marathon, a race whose organizers hope its prestige, reputation and tradition will continue to make it attractive.

"Appearance money is something I don't think we'd get into, either," Morse said. "We want to preserve the amateur status."

Said Greg Meyer, the 1983 winner: "I think Boston has been getting by on the perception that it's the best race, but it will continue to lose good runners if it doesn't give prize money."

Of the world's elite marathoners, only defending champion Geoff Smith is competing here this year. Other runners have chosen to participate during the next few weeks in races in Pittsburgh, New Jersey, London and Japan, all of which offer money.

Smith, 31, of Liverpool, England, is a heavy favorite among approximately 5,800 runners, nearly 1,000 fewer than last year, when he won by more than four minutes in 2 hours 10 minutes 34 seconds.

His strongest competition is expected to come from Kevin Ryan of New Zealand and Americans Dan Dillon and Gary Tuttle.

The men's field was further weakened by two events of the past week: No. 5 seed Mark Plaatjes of South Africa flew to Boston only to be ruled ineligible because of an international rule forbidding the entry of athletes from his country, and No. 6 Carlos Godoy of Colombia withdrew after published reports that he falsified his qualifying-time information.

An equally weak women's field is led by Lisa Larsen Weidenbach, a 23-year-old from Marblehead, Mass., who placed fourth in the U.S. Olympic Trials and won the Nike Cherry Blossom 10-Mile race here two weeks ago. Her only competition appears to be Karen Dunn of Durham, N.H. Two fine women runners, Laura DeWald Albers and Jenni Peters, withdrew Thursday.

One notable change for this year's race will be at the starting line in Hopkinton. It will be 47 yards farther back than in the past, to meet the guidelines for course length newly established by The Athletics Congress, the national governing body for amateur running.

One of the most noteworthy runners will be John A. Kelley, 77, of East Dennis, Mass., who won in 1935 and 1945 and will be competing here for the 54th time.

Bennett Beach of Bethesda has run the race every year for the past 17 years and is hoping to eventually better Kelley's feat of 23 straight Boston Marathons. "I have a long way to go," Beach said, "but my goal is to run it every year and finish every year."