The effect of oxidative stress on the process of spermatogenesis in terms of hsp70 expression was studied. For creating different oxidative stressed mice, three selenium (Se) levels viz., deficient (group I), adequate (group II) and excess (group III) were fed for 8 weeks in a yeast-based diet. After completion of diet feeding, Se level was significantly decreased in group I and significantly increased in group III, as compared to group II. Glutathione peroxidase (GSH-Px) activity was significantly decreased in both liver and testis in group I animals; however, the activity was comparable in groups II and III. Significant increase in the testis glutathione-S-transferase (GST) activity was observed in group I. No change was seen in group III, when compared to group II. Histological analysis of testis revealed a significant decrease in the germ cell population in group I, as compared to group II, with a predominant effect on spermatid and mature sperm numbers. In group III, displacement of germ cell population was observed. ELISA assays for hsp70 level showed increase in group I as compared to group II, whereas no significant change was observed in group III, as compared to group II. Immunohistochemical analysis revealed intense localization of hsp70 only in spermatid and sperm cells. The expression in groups II and III was homogeneous with slightly increased expression around lumen in group III. The data indicate that excessive oxidative stress in Se deficient group, affects the spermatogenesis process, especially affecting the mature sperm number which in turn leads to infertility.