Grete Waitz of Norway won the women's marathon to earn the first gold medal at the inaugural World Track and Field Championships today.

Ernesto Canto of Mexico won the 20-kilometer walk and Edward Sarul of Poland gained the gold medal in the men's shot put. But there were no victories for Cuba's Alberto Juantorena or Italy's Sara Simeoni.

Juantorena, who won gold medals in the 400 and 800 meters in the 1976 Olympics, fractured a bone and ruptured a ligament in his right ankle in a fall after he crossed the finish line in second place in an 800-meter heat.

As he came to the line he looked back and appeared surprised to see Juna Ndiwa of Kenya just behind him. He turned back, crossed the line but lost his balance and hit a plastic box at the side of the track.

"I was hit from behind," he said.

Juantorena, 31, underwent surgery and will be in a cast for four to six weeks. He will undergo rehabilitation for three months, said Dr. Timo Silvenoinen of nearby Toolo Hospital.

"I feel perfectly well now, and I will begin training as soon as I can," he said. "That means in about a year, because I want to go to Los Angeles in 1984 (for the Olympic Games). My career is not finished: all to the contrary."

Simeoni, a former world record holder in the women's high jump, failed to qualify for the finals because of a pulled left calf muscle.

Waitz waved to the capacity crowd of 53,000 at Olympic Stadium as she crossed the finish line. She completed the marathon in 2 hours 28 minutes 9 seconds. Marianne Dickerson of the United States, competing in only her third marathon, overtook Raise Smekhnova of the Soviet Union in the final straightaway to place second in 2:31.09, four seconds ahead of Smekhnova.

Waitz's winning time was more than five minutes slower than the world record of 2:22.43 held by Joan Benoit, who is injured and did not compete.

But Waitz, 29, who has won four New York City Marathons, was still pleased.

"The race went very well, even though the course was heavy," she said. "I knew I could make it at about seven to eight kilometers from the finish. Everything went according to my tactics."

Smekhnova's tactics, however, were less than perfect.

"I thought I still had one lap to run when I came into the stadium and did not respond to Dickerson's finish," she said.

Canto finished the walk in 1:20.49, 10 seconds ahead of European silver medalist Jozef Pribilinec of Czechoslovakia. Evgeny Evsiukov of the Soviet Union finished third at 1:21.08.

Sarul won the shot put at 70 feet, 2 1/4 inches. Ulf Timmermann of East Germany was second at 69-5 1/4, followed by Remigus Machura of Czechoslovakia with 68-10.

There were no surprises in the men's 100 meters. The three American favorites--Carl Lewis, Calvin Smith and Emmit King--each won two heats to reach the semifinals.

Lewis easily won his second heat in 10.20 seconds, the fastest time of the day. Smith, the world record holder, was clocked at 10.27.

Smith, who set a world record of 9.93 in the high altitude in Colorado Springs, Colo., last month, said he was "relaxed in the first round this morning and the second round was comfortable, too.

"The worst part of my race is having to use the starting blocks, and I am going to need a good start to beat Lewis."

The women's 100 meters stayed to form as all the favorites easily advanced, including world record holder Evelyn Ashford.

Ashford beat East German rival Marlies Gohr in the second round; the two are favorites in Monday's final. Ashford was the fastest of the 16 semifinal qualifiers, winning her second-round heat in 11.11. Gohr was timed in 11.16.

Ashford, who has had a stomach virus the last few days, pulled up after finishing and started limping. But she smiled to photographers, waved and walked back to the grandstand.