OBJECTIVE: To evaluate the potential protective effects of Ginkgo biloba on developing testes exposed to chronic hypobaric hypoxia during their prenatal life. STUDY DESIGN: Twelve pregnant Wistar albino rats on the fifth gestational day were placed in hypoxic chambers for the upcoming 15 days. Six pregnant female rats were kept under normal atmospheric conditions during the pregnancy as a control group. The study groups were as follows: Control, Hypoxia, and Hypoxia+Ginkgo biloba. Ginkgo biloba was administered for each designated postnatal sacrifice day. For the Hypoxia+Ginkgo biloba group, after birth, 100 mg/kg of Ginkgo biloba extract was administrated orally to the newborn male rats. Testes tissues were sampled on postnatal days 7, 14, and 21 from each group, and PCNA, TUNEL, and TEM examinations were performed. RESULTS: PCNA immunoreactivity was decreased and TUNEL positive cell number was increased in the hypoxic group. TEM examination revealed degenerative changes in hypoxic group testes tissue. Hypoxia changed the cell cycle in spermatogenic series by reducing proliferation and increasing apoptosis. Spermatogenic cell degeneration and high Leydig cell activity were determined in the hypoxia group by TEM examinations. CONCLUSION: We believe that Ginkgo biloba has protective effects on testes tissue, especially in longterm use. © Science Printers and Publishers, Inc.