Objectives: As pesticides hold a unique position among environmental contaminants; the objective of the present study was to evaluate the toxic effects of Isoproturon, a substituted phenylurea herbicide on testis of albino rats. Methods: The compound, suspended in groundnut oil, was administered orally to rats for 60 days at the doses of 400 mg/kg and 800 mg/kg body weight for two groups respectively. Body weight, testis weight and seminiferous tubular diameter were measured. Histological study was done on haematoxylin- eosin stained 5__ampersandsignmu;m thick paraffin sections. Results: Decrease in weight gain and seminiferous tubular diameter was observed in experimental rats which was highly significant. The difference in testis weight was not significant statistically in experimental group as compared to control group. Light microscopic study showed degenerative changes in the testis. Conclusions: Degenerative changes in the gametogenic cells indicate adverse effects on the functional ability of these cells and are highly conclusive of reproductive toxicity caused by isoproturon.