|To investigate the cadmium (Cd) toxicity on the testis, male rats were treated with 1, 2, 4 and 8 mg/kg of Cd by IP. According to histochemical studies, Cd-treated testis tissue showed death of spermatozoa, death of Sertoli cells, death of all the spermatogenic cells, and finally disappearance of basal lamina of seminiferous tubules with increasing doses, and showed decreased ground substances and Leydig cells, increased inflammatory cells and fibroblasts, and finally disappearance of ground substances and all the cells except fibroblasts within interstitial tissues with increasing doses. Accord-ing to biochemical studies, two kinds of proteins, 25 and 45 kDa, were dramatically disappeared from the total protein of rat testis treated with Cd comparing to normal testis. The result of electrophoresis of total protein suggests that actin (45 kDa), presumed on its molecular weight and amount, in the testis-cells is the primary target of Cd poisoning. Although its exact mechanism is not clear, the disap-pearance of two proteins when testis is exposed to Cd should give some clues to understand the mech-anism of necrosis of testis tissue crumbling by heavy metal pollutant such as Cd.