The present study was designed to evaluate the possible induced molecular damage on the DNA of the testes' cells and leucocytes, after the oral administration of oseltamivir phosphate "tamiflu", which is used as anti-influenzal drug. Forty male adult albino rats (Rattus norvegicus) were used in this study. The testes were the organ of choice in the present work since the drug's effects on the male reproductive system has gained increasing importance over the past two decades, in addition to the leucocytes. The therapeutic scheme, minimum and maximum protective schemes of tamiflu applied to humans were converted to their correspondents in the rats. The rats were divided into 4 groups, 10 rats in each group, as follows: Group I: Negative control group. Group II: The rats were given the therapeutic scheme (1.35 mg/kg) of tamiflu twice/day for 5 consecutive days. Group III: The animals were given the short-term prophylactic scheme of tamiflu (1.35 mg/kg, once/day for 10 days), and Group IV: The rats treated with the long-term prophylactic scheme of tamiflu (1.35 mg/kg, once/ day for 45 days). The rats in the afore-mentioned groups were killed one day after the last dose by severing the neck blood vessels and the testes were dissected out and cut into pieces and were prepared for DNA gel electrophoresis. Besides, heparinized blood samples were collected immediately for the study by using the Comet assay.