Top-seeded Ivan Lendl was upset in men's singles and Andrea Jaeger defaulted in the women's competition of the $200,000 Gunze World tennis tournament yesterday in Kobe, Japan.

Lendl, winner of 15 of 18 tournaments since last year's U.S. Open, lost to Vijay Amritraj, 7-6, 3-6, 7-5, in the semifinals. Amritraj will meet No. 2 seed Sandy Mayer in today's title match at Kobe's central gymnasium. Mayer advanced at the expense of Vince Van Patten, 6-0, 7-6.

Jaeger was trailing, 2-3, in the first set to semifinal opponent Kathy Jordan when back pains made her give up her chance to win the first-place money of $30,000 for the second straight year. A Japanese doctor examined Jaeger and said she needs a three-week rest; no need for her to be hospitalized.

Tracy Austin, seeded No. 1, defeated Pam Shriver, 7-5, 3-6, 6-3, and confronts Jordan today . . .

Meanwhile, top-seeded Chris Evert Lloyd was breezing in a 61-minute semifinal of the Swiss Women's Open of the Toyota Series, 6-0, 6-1, over No. 4 seed Virginia Ruzici. Her opponent today will be Andrea Temesvari, 16, of Hungary. Unseeded in the tournament, Temesvari eliminated Yvonne Vermaak, 7-5, 6-4. Of the big opportunity that set up, she said: "I'm so excited . . . I think Chrissie is the best player in the world . . . But there won't be any pressure on me, so I will just try" . . .

In the $250,000 German Open at Hamburg, Jose Higueras and defending champion Peter McNamara made it to today's final of the Volvo Grand Prix event. Higueras ousted Gene Mayer, 6-2, 6-2, 6-2. McNamara took out Andres Gomez, 7-5,6-1,6-2.