We performed experiments to determine whether treatment with vitamin D or 1,25-dihydroxycholecalciferol could reverse male infertility caused by vitamin D deficiency. Additionally, an attempt was made to distinguish between a direct and an indirect effect of 1,25-dihydroxycholecalciferol on reproductive tissue. Vitamin D-deficient male rats with impaired fertility were treated with vitamin D and 1,25-dihydroxycholecalciferol for 3 wk, then mated. Secondly, vitamin D-deficient male rats were made normocalcemic by increasing dietary calcium, and their fertility was compared with that of vitamin D-deficient, hypocalcemic rats. The fertility of male rats was restored by treatment with either vitamin D or 1,25-dihydroxycholecalciferol. However, fertility was also restored in vitamin D-deficient animals by feeding them a diet supplemented with high levels of calcium. These results indicate that the influence of vitamin D and its active metabolite, 1,25-dihydroxycholecalciferol, on male fertility is indirect. Vitamin D and 1,25-dihydroxycholecalciferol seemed to influence male fertility by acting on classic target tissues and regulating levels of calcium in reproductive tissues.