Greg Foster and Willie Gault of the United States finished one-three today in the men's 110-meter hurdles final at the World Track and Field Championships. Foster, despite knocking down the last three barriers and almost falling, won the gold medal in 13.42 seconds.

"I don't know how I kept going," Foster said after one of the most dramatic finishes in the week-long competition. Arto Bryggare of Finland was second, four-hundredths of a second behind Foster.

"I was doing fine until the eighth hurdle," Foster said. "I charged it, hit it hard and lost my stride. I also hit No. 9 pretty hard, but it was the eighth that threw me off. The most important thing was that I won."

Gault's time was 13.48. "I am not happy or satisfied, but at least I got a medal," said Gault, who is trying to make up his mind whether to sign with the Chicago Bears of the National Football League or stay eligible for the 1984 Olympics. (Story, Page D2.)

The United States also earned a silver medal when Tyke Peacock of Fresno, Calif., finished second in the men's high jump to 19-year-old Gennady Adveenko of the Soviet Union. Peacock matched Adveenko's height of 7-7 1/4, but had more misses.

World record holder Zhu Jianhua of China took the bronze at 7-6. Dwight Stones of the U.S. also was at 7-6, but made more attempts at the height. The Naval Academy's Leo Williams was 12th at 7-3 3/4.

East Germany, Britain and Czechoslovakia won the day's other three finals. The U.S. leads the overall medal standings with 19, but trails East Germany in golds, 7 to 6.

East German sprinter Bettine Jahn won the women's 100-meter hurdles with a world best 12.35 seconds, but the record was not allowed because her run was wind-assisted.

Briton Daley Thompson, the 1980 Olympic champion and former world record holder, won the decathlon, totaling 8,666 points. The silver medalist was West German Juergen Hingsen, who set the world mark (8,777) this year. He totaled 8,561 here.

Tiina Lillak gave home fans their first gold medal by winning the women's javelin on a throw of 232 feet 4 inches. Karen Smith of Venice, Calif., was far off the pace in ninth place with a throw of 196-1.

Lillak was ecstatic after her winning throw. She raced around part of the field, raising two fingers into the air in a victory sign and beamed broadly to the wildly cheering crowd.

The fans reacted by yelling, "Tii-na, Tii-na."

U.S. prospects for gold in Sunday's final program seem excellent.

Carol Lewis of Houston, attempting to join her brother Carl as a gold medalist, was the leader in the best women's long jump semifinal after inserting contact lenses for a better look at the takeoff point. Her best jump was 22-3.

In the men's 1,500-meter semifinals, Steve Scott of Scottsdale, Ariz., was the only American to make the final, with a time of 3:36.43. The event shapes up as a classic, with Steve Cram of Britain gaining the final in 3:35.77 and countryman Steve Ovett a fraction back at 3:36.26. John Walker of New Zealand (3:36.52) and Mike Boit of Kenya (3:37.75) also made it to the final.

"I think Scott will win it, very easily," said South African-born Sydney Maree, who failed to gain the final.

Scott wasn't so confident. He said Cram would be among his toughest opponents, but added, "You can never underestimate Ovett. He is too good of a champion."

Calvin Smith of Bolton, Tex., advanced to the men's 200-meter final with the fastest semifinal time--20.29 seconds. Elliott Quow of Brooklyn was fourth-best in another heat at 20.69 and also reached the final.

In the women's 200-meter semifinals, Florence Griffith of Los Angeles had the fastest time, 22.41 seconds. The men's and women's 400-meter relay teams also turned in outstanding clockings.

The men's team was timed in 3:02.13 and the women's team was timed in 3:26.82.