Effect of single oral dose (90 mg/kg body weight), multiple doses (90 mg/kg body weight for 7 days) or even higher doses (180-300 mg/kg body weight) of alpha-chlorohydrin on the testis-epididymis complex of dog, rat, cryptorchid rat, hedgehog, domestic fowl, lizard, frog, and toad has been studied. alpha-chlorohydrin treatment, at any dose, did not induce lesions in the testis-epididymis complex of dog and hedgehog having testis in scrotum and inguinal canal respectively. Abdominal testis of cryptorchid rat, domestic fowl, lizard, frog and toad also did not respond to alpha-chlorohydrin treatment. Lesions in normal rat testis-epididymis complex, after single oral dose of alpha-chlorohydrin, were quite prominent. Non-sensitivity of alpha-chlorohydrin to these animal species may be due to the absence of the pampiniform plexus complex in hedgehog and sub-mammalian animal species. Absence of conventional epididymis in the sub-mammalian animal species may be the additional reason of the non-sensitivity of the drug. Prominence of collateral blood vasculature in dog testis-epididymis complex and some alterations in the blood supply due to cryptorchidity in cryptorchid rat testis seems to be the reason of non-sensitivity of alpha-chlorohydrin to dog and cryptorchid rat testis. These observations confirm the hypothesis that the action of a single oral dose of alpha-chlorohydrin is associted with the blood vasculature of the testis-epididymis complex.