Petra Schneider set a world record of 4:36.10 in the 400-meter individual medley as East Germans won the first two women's events at the World Swimming Championships today. She beat her own record of 4:36.29, set in July 1980.

Schneider easily beat archrival Tracy Caulkins, who brought the United States only a bronze medal, behind Kathleen Nord, also East German.

Birgit Meineke won the women's 100-meter freestyle. Jill Sterkel of the U.S. was third.

Steve Lundquist won the 100-meter breaststroke for the U.S. but Michael Gross of West Germany upset world-record holder Rowdy Gaines in the 200 freestyle in initial men's finals.

The preliminaries on this first day of competition were marred by a protest by the United States and Sweden after Rich Saeger (U.S.) and Pelle Holmertz stopped in the middle of a 200-meter freestyle heat. They claimed that the starting horn fouled up, but the protest was disallowed by the International Swimming Federation.

"I don't know why they use a gun and a horn," Mark Schubert, the U.S. coach, said. "In most meets, in the United States or anywhere in the world, they use a gun or a horn, but not both."

Ray Essick, executive director of the U.S. Swimming Federation, said the horn starting sound would be eliminated for the rest of the championships. He said there was "considerable evidence of a mechanical malfunction."