Twenty-seven patients cured of advanced testicular cancer by cisplatin-based chemotherapy have been assessed, a median of 30 months after start of treatment, for the long-term effects of such treatment on renal, endocrine, audiometric, reproductive and respiratory function. To control for the effects of orchidectomy on endocrine function a similar group of 11 patients cured by orchidectomy alone was also assessed. The extents of impairment in hearing and renal function were related to the total dose of cisplatin received, while the majority of patients had respiratory impairment which was, in part, related to the total dose of bleomycin. TSH was significantly higher in the chemotherapy group although serum free thyroxine and free T3 were normal in all. FSH was raised in 67% of the chemotherapy group although serum free thyroxine and free T3 were while LH was raised in 75% and 45% respectively. Serum testosterone was normal in all. The levels of FSH and LH were both independently correlated with age of the patient while FSH was higher in patients having more chemotherapy and had a tendency to fall towards normal with time since treatment. Over half the patients had normal sperm concentrations although 74% had a raised proportion of abnormal sperm. Indices of sperm function were worse in patients having more chemotherapy but sperm number increased towards normal with time since treatment, particularly after the second year. The long-term side-effects of chemotherapy for testicular cancer are thus generally mild but are largely irreversible and their severity is related to the total amount of chemotherapy received. As their longer term significance is not clear we would recommend that, in the treatment of testicular cancer, doses of chemotherapy are reduced to the minimum required for cure. Assessment of long-term side-effects of chemotherapy for testicular cancer should be a mandatory part of any study of such treatment and should be considered in any comparison of different therapies.