Qualifier Jana Pospisilova of Czechoslovakia upset second-seeded Helena Sukova, also of Czechoslovakia, 6-3, 6-3, Thursday in the second round of the $200,000 European Indoor women's tennis tournament at Zurich, Switzerland.
Pospisilova, 18, is ranked No. 124, while Sukova is sixth.
"It was my biggest success so far," said Pospisilova, who lost this year's European Junior final to Conchita Martinez of Spain.
In other matches, top-seeded Pam Shriver downed Jonna Jonerup of Sweden, 6-0, 6-3; Brenda Shultz of the Netherlands defeated Dinky Van Rensburg, 6-4, 2-3, retired, and eighth-seeded Raffaella Reggi of Italy beat Wiltrud Probst of West Germany, 6-2, 4-6, 6-2.
Second-seeded Boris Becker of West Germany struggled past Carl-Uwe Steeb, also of West Germany, 6-7, 6-1, 6-2, and advanced to the quarterfinals of the Seiko tournament at Tokyo.