Top seed Jim Courier beat Francisco Michelotti and No. 2 seed Andrey Cherkasov defeated Nicolas Pereira in boys 18 matches at the Orange Bowl International Tennis Championships in Miami Beach, Fla.

Courier of Dade City advanced with a 6-2, 6-1 victory over his Italian opponent. Cherkasov of the Soviet Union outlasted the Venezuelan No. 9 seed, 7-6 (9-7), 6-7 (5-7), 6-4.

Courier will meet Sweden's No. 10 seed Magnus Zeile in the semifinals today. He beat No. 3 Alejandro Aramburu of Peru, 1-6, 6-2, 7-5. Cherkasov plays Ivory Coast's Clement N'Goran, who beat Italy's No. 12 Renzo Furlan, 6-4, 6-2.

In girls 18 quarterfinals, the Soviet Union's top-seeded Natalia Zvereva beat Maria Strandlund of Sweden, 6-1, 5-7, 6-4. Today, she meets No. 14 Deborah Graham of Fountain Valley, Calif., who defeated No. 11 Carrie Cunningham of Livonia, Mich., 3-6, 6-4, 6-1.

In the other girls 18 semifinals match, Italy's Laura Lapi will face No. 15 Elena Brukhovets of the Soviet Union. Lapi beat No. 3 seed Gabriella Mosca of Argentina, 6-3, 6-3. Brukhovets reached the semifinals with a 5-7, 6-2, 6-3 victory over Canada's Jane Yates.