Now there can be no doubt about it: Alberto Salazar is as great as his word. And Allison Roe is a lot better than hers.

Last year, Salazar said he would run 2:10 in his first marathon. And he did. This year in the New York City Marathon, he said he would break Derek Clayton's world record (2:08.33:6 set in l969). And today, he did.

"I opened up my big mouth again this year," Salazar, 23, said after breaking Clayton's record today by 20 seconds in 2:08.13. "I had no choice," said the native of Cuba, who in June was graduated from the University of Oregon.

Roe, who had been treated Friday for tendinitis in her right ankle, refused to predict her time, much less a record. She was allowed in the race only after pledging to put her winnings from a recent race in Eugene, Ore., into a trust fund. Two days ago, she took the day off; Saturday she jogged; today she broke the women's world record in 2:25:28.74. Grete Waitz, who ran 2:25:42 here last year, had held the record.

"I wasn't shooting for it," said Roe, 24, of New Zealand, who won the women's division of the Boston Marathon last April. "I just wanted to be competitive, whether it was 2:30 or 2:40; it didn't matter."

What did matter was that just about the time she was crossing the finish line, Waitz was getting back to her hotel. Shin splints forced the defending champion out of the race at a water station before the Queensborough Bridge. She borrowed some money and took a cab home.

Waitz, who had won the last two New York City marathons, setting world records each time, was in pain almost from the beginning. After eight miles, she knew she couldn't finish. The loss of her world record, she said, did not pain her. "I'm not so unhappy about that," she said. "I only wish I had been able to defend it."

Waitz wasn't the only former champion missing in action. Bill Rodgers, who won four straight in 1976-79, never made it to the starting line although 14,496 others did. According to Peter Diamond, a producer for ABC television, Rodgers phoned him at 11:50 p.m. Saturday to say that his financial arrangements had fallen through and he would not run. Rodgers was not available to comment yesterday.

The day began with low-slung clouds and high-strung crowds, estimated at 2 1/2 million people, swollen perhaps by the chance to be seen on network television. Most of them were mannerly. "A few times a few people got overexcited," Salazar said. "They would run out and grab us. One tried to give me a beer."

Another tried to stuff a dollar bill down the shirt of John Graham, an early leader. Another tripped Julie Brown, the early women's leader, after she had run eight or nine miles.

The crowds were particularly unruly early in the day, when the pack was most crowded and in Brooklyn. Louis Kenny of Ireland opened up an early 75-yard lead over a group of 35 runners, including Salazar, and set a relatively swift pace. But just past the 10-mile mark (they were 10 seconds off world record pace), Salazar, Graham, Rodolfo Gomez of Mexico, Jose Gomez of Mexico and several others caught up with Kenny.

They clung together the next five miles, across the Queensborough Bridge and past the 15-mile mark. But as they left the bridge and ran onto First Avenue, Salazar and Jose Gomez, who was running his first marathon, passed beneath an arbor of red, white and blue balloons, leaving the others as a backdrop against slate skyline.

They ran side by side, jockeying for the lead, up First Avenue and past the bistros blaring Frank Sinatra's "New York, New York."

At 86th Street, a sign in the crowd with a pair of skinny runner's legs on it, proclaimed, "Go for it," and Salazar did. Between miles 16 and 17, he ran a 4:33 mile and broke away from Jose Gomez, his final pursuer (Gomez eventually finished 36th) between 16 and 19 miles. Salazar averaged 4:43 a mile, and at the 19-mile mark, he had a 23-second lead over Rodolfo Gomez of Mexico, who eventually finished seventh.

Salazar said he wasn't aware he was burning rubber. "He (Jose Gomez) started to push around l6," Salazar said. "Every time I tried to take the lead, he accelerated. But I looked at him and he didn't look too good. At l8, I decided I had to push it if I was going to get the record, so I picked it up."

At 20 miles, Salazar knew he had the record, that it was merely a question of "maintaining the record pace," of "not settling for the win." The crowd wouldn't let him. "They kept reminding me," he said. After all, a promise is a promise.

The only thing he didn't beat was the computer that had predicted he would finish in 2:07.51. At 2:07.40, the band in Central Park started to play. At 2:07.48, the crowd began to whistle. At 2:07.49, the motorcycle escort passed the finish line. And at 2:08.13 Salazar, who knew he would get the record but "was waiting for the one minute when I could see it (on the scoreboard) myself," saw it happen.

At 3:07, Salazar was composed and "feeling very relieved." After Clayton set the record in 1969, he said he felt his head had been severed from his body, even though some people said he went so fast because the course was a bit short.

"Maybe that's the way he felt that way," Salazar said. "I commend him if that's how hard he pushed himself. For 20 minutes last year, I felt bad. Now I feel fine. I don't face six months of feeling wiped out."

In second place was Jukka Toivola of Finland in 2:10.52, followed by Hugh Jones of England (2:10.59) and Nick Braun of England (2:11.09). Edward Swiatocha of Arlington, Va., had the best time among a large contigent of Washington-area runners, finishing 49th in 2:19.54.

Race organizers said 14,496 runners competed and 13,360 finished. The last to finish was Barry Weisberg, an assistant district attorney in Brooklyn, whose time was 7:34.13.

Like Salazar, Roe took the lead on First Avenue. For the first three miles, her ankle was feeling touchy. And from the beginning she was content to let Brown lead, to remain with Waitz, the woman to beat.

Roe said that at 12 miles, "Grete cut out of the race. Suddenly she took off into a side street. But soon she was back on pace," Roe said. "After 22 kilometers (about 14 miles), she spoke to me and she said she was going to (have to quit)."

"I said," Waitz said, "go get her."

At l6 miles Roe took her advice. She took the lead from Brown just over the Queensborough Bridge, and after that it was a question of "making an effort to keep up with the men." New York was fine she said. But the roads were not so good.

Mayor Edward Koch, sitting at her side after the race, smiled and said: "We built them that way."

Seven blocks from the finish line she appeared to be lagging. A man in a green warmup suit stopped to look as she went by, and the TV people said: "She's going to have to pick it up if she's going to break the record."

It was as if she heard him. She passed one, two, five, men, and then the finish line. Ingrid Kristiansen of Norway was second, almost a mile behind (2:30.08), and Julie Shea of Raleigh, N.C., was third (2:30.11). Brown of Santa Monica, Calif., faded to ninth in 2:40.48.

When all the questions were finished, Roe was asked about her next objective. She said it is to sit on a beach in New Zealand or Honolulu.

The same question was put to Salazar, who never hedges when making predictions. "My next objective," he said "is to get married in December."