Deltamethrin (DM) is a alpha- cyano pyrethroid insecticide used extensively in pest control. Although initially thought to be least toxic, a number of recent reports showed its toxicity in mammalian and non-mammalian laboratory and wildlife animal species. The present study, carried out in male rats, is a contribution to explore some mechanisms underlying DM toxicity. The aim of the present research was to investigate the effect of different subcutaneous treatments with DM (2 ppm for 30 days, 20 ppm for 45 days and 200 ppm for 60 days) on testes histopathology, sex hormones and oxidative stress from male rats. Our study mentioned an hypospermatogenesis within the testes accompanied by some apoptotic figures in particular cell fragments into the seminiferous tubules (ST)' lumen. The results obtained show that follicule-stimulating hormone (FSH), luteinizing hormone (LH) and testosterone can be differently influenced in rats. In fact, findings of the present investigation mention a significant decrease (p < or = 0.05) of FSH, LH and testosterone at the highest DM dose. Whereas a significant reduction of FSH was noticed after 45 days of treatment. The assessment of oxidative stress by malondialdehyde (MDA) measurements in plasma revealed a significant increase of this parameter after 30 days, 45 days or 60 days. In conclusion the study shows that subcutaneous DM treatment produces an arrest of spermatogenesis, a significant disharmony in sex hormones and MDA levels in rats that is related to dose, length of treatment and to the lipid peroxidation which may be one of the molecular mechanisms involved in DM-induced gonads toxicity.