The deleterious effect of cadmium on the testis has been ascribed to failure of regulation of the testicular temperature by the pampiniform plexus (Turner, 1966) and cadmium-induced damage to the capillary endothelium (Maekawa, Tsunenari & Kurematsu, 1966; Gunn, Gould & Anderson, 1963). Our recent findings in the rat of an early differential effect of cadmium on the scrotal and contralateral cryptorchid testes in the same individual do not entirely support the theory implicating the pampiniform plexus as the site of cadmium action (Chatterjee & Ray, 1972). The higher rate of incorporation of tritiated lysine in a cryptorchid testis compared to its scrotal counterpart (Davis, 1965) suggests that the abdominal temperature may cause an initial heat-induced vasodilatation of the spermatic vasculature and thereby augment the blood flow through the cryptorchid testis (Glover, 1965). This paper describes our findings concerning the effect of reserpine or adrenalectomy in preventing an early detrimental and