Copper chloride treatment adversely affects testicular activity in albino rats. To investigate its antitesticular effects mature (120 days) Wistar strain albino rats were treated intraperitoneally (i.p.) with copper chloride at doses of 1000, 2000 and 3000 μg/kg body weight/day for 26 days. Significant reduction of testicular and accessory sex organs (seminal vesicle, ventral prostate) weight, along with inhibition of testicular Δ5-3β-hydroxysteroid dehydrogenase (Δ5-3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD) activity and reduction in plasma testosterone level, were observed at the doses of 2000 and 3000 μg/kg body weight/day. The degree of inhibition in all the parameters were increased with the increase of dosage. But no significant change was observed in the above parameters when the animals were treated with 1000 μg/kg body weight/day dose. This suggests that copper produces a suppressive influence on male reproductive activity, mainly on testicular weight and steroidogenesis and accessory sex organ weight in a dose-dependent manner.