1. The effect of an acute testicotoxic dose of cadmium (CdCl2.H2O, 2.0 mg/kg i.p.) on liver morphology and drug-metabolizing enzyme activities were studied in adult male and female rats. 2. Cd treatment to female rats caused a slight and reversible decrease in hepatic microsomal aryl hydrocarbon hydroxylase (AHH) and aminopyrine N-demethylase (APND) activities. 3. No significant changes were noted in the liver morphology, serum alanine aminotransferase activities, enzyme induction by phenobarbital and 3-methylcholanthrene, and glucuronosyl-transferase (GT) and glutathione S-transferase (GST) activities. 4. The same Cd treatment to male rats, however, resulted in a much more pronounced and prolonged reduction in AHH and APND activities, which was attributable to a Cd-induced testicular necrosis and, hence, impairment of androgen secretion. 5. Accordingly, Cd treatment to castrated male rats did not lower the enzyme activities any further, and full recovery of activities was obtained after the administration of testosterone. 6. Both GT and GST, the two sex-independent enzymes, were not significantly affected by either Cd or gonadectomy in the male rat. 7. The present data show that a low acute dose of Cd induces chemical castration without severely altering hepatic function.