Gonadal function was studied in 15 patients 12 pubertal or postpubertal, and three prepubertal, who had been treated during childhood for nonmetastatic osteosarcoma of the long bones by chemotherapy regimens that included cis-platinum and adriamycin. Of seven postpubertal female patients assessed (mean age at diagnosis 16.5 years), three were amenorrhoeic and showed evidence of ovarian damage with raised gonadotrophin levels and a low serum oestradiol concentration. One patient who had regular periods had a raised luteal-phase follicle-stimulating hormone (FSH) concentration suggestive of gonadal dysfunction. Severe oligospermia or reduced testicular volumes in the presence of raised gonadotrophin levels were observed in three of the five pubertal males (mean age at diagnosis 13.25 years). A reliable assessment of gonadal function was not possible in three male patients who remained prepubertal at the time of study. The median total dose of cis-platinum received by those patients with gonadal damage (median dose, 490 mg) was significantly higher than in those patients with normal gonadal function (median dose, 300 mg) (P = 0.01). In the boys the damage to the testes was primarily directed at the germinal epithelium. Leydig cell function was intact and the males progressed spontaneously through puberty. In the girls, unlike the boys, there was evidence of reversibility of gonadal damage with time. This is the first study to show gonadal dysfunction due to cis-platinum and adriamycin therapy in childhood.