We investigated the spermatogenic function of patients with testicular cancer, and the influences of anti-cancer chemotherapy on testicular function in these patients. Fifty-one patients with testicular cancer were selected for evaluation of their testicular function, including spermatogenesis and endocrinological function, before and after chemotherapy with anti-cancer agents. Before chemotherapy with anti-cancer agents, 22 of 49 patients (44.8%) had a sperm concentration of less than 20 x 10(6)/ml, and 8 patients (16.3%) showed azoospermia. The mean sperm concentration of the patients with testicular cancer was 29.0 x 10(6)/ml before therapeutic chemotherapy with anti-cancer agents, but within 3 months after chemotherapy, it decreased to 3.86 x 10(6)/ml (p < 0.01). Fifteen of 19 patients (73.7%) were revealed to have azoospermia. Damage to spermatogenesis became more severe with the number of chemotherapy treatment. No patients had a detectable sperm count at the completion of 3 or more courses of chemotherapy. But some patients who received 3 courses or more of chemotherapy showed recovered sperm counts after 2 or more years. Thus, a lack of sperm after chemotherapy for cancer did not necessarily indicate inability to recover spermatogenesis over 2 years after chemotherapy. Serum FSH levels of the patients were 5.62 +/- 3.43 mIU/ml before chemotherapy, and 19. 70 +/- 17.06 mIU/ml (p < 0.05) at the time of its completion. Serum FSH levels could reflect damage to spermatogenesis in these cases. Cases in which spermatogenesis did not recover may have higher serum FSH levels than those with recovery of spermatogenesis.