Metalaxyl is a benzenoid fungicide used to control soil-borne fungal diseases on fruits, cotton, soybean, peanuts, ornamental and grasses. The present work aims to evaluate the effect of oxidative stress on the induction of apoptosis in thymocytes of mice by metalaxyl. The work extends to study the possible role played by antox in minimising the toxicity of metalaxyl. Thymus of metalexyl-treated mice showed many histopathological alterations. There was a loss of differentiation between region of cortex and medulla, abnormal arrangement of lymphocytes and degeneration of the trabecula. Treatment with metalaxyl leads to an increase in apoptotic rate of thymocytes as detected by flow cytometry. Moreover, metalaxyle administration to animals increased significantly malondialdehyde and decreased catalase activity. The results showed that treating animals with metalaxyl followed by antox revealed an improvement in the histological changes observed in animals treated with metalaxyl alone. Moreover, antox treatment leads to a decrease in the percent of apoptotic cells. A decrease of malondialdehyde level and increase of catalase activity was recorded.