Previous reports have demonstrated that cadmium- (Cd-) induced testicular necrosis is an age-dependent process. However, little information exists on age-related intestitial cell (IC) damage in the rat after acute exposure to Cd. In vitro and in vivo measures of testicular damage were utilized to compare the sensitivity of these measures and to further investigate age-related Cd-induced testicular damage. Testes, epididymides, and seminal vesicle weights, serum testosterone (sT), hCG-stimulated sT, and basal and stimulated IC testosterone (T) production were compared in rats 21 d following an injection of 2 mg Cd/kg at 9, 37, 67, and 97 d of age. The only Cd-related change noted for immature rats was an 84% reduction in sT. In rats injected when 37 d old, hCG-stimulated sT and epididymides and seminal vesicle weights, although depressed, were not significantly altered. However, all other measurements were significantly depressed. All measures of testicular damage were significantly depressed in rats injected at 67 and 97 d of age. Overall, in vitro measures were more sensitive indicators of Cd-induced testicular damage than in vivo measures.