The efficacy and safety of highly purified follicle stimulating hormone (FSH) associated with human chorionic gonadotrophin (HCG) was studied in 60 men with hypogonadotrophic hypogonadism. Of these men, 16 suffered from Kallmann's syndrome, 19 from idiopathic hypogonadotrophic hypogonadism and 25 from hypopituitarism. Basal testosterone concentrations were found to be far below the normal range. At baseline, 26 patients were able to ejaculate and all of them showed azoospermia, while the remaining patients were aspermic. All patients self-administered s.c. injections of FSH (150 IU x three/week) and HCG (2500 IU x two/week) for at least 6 months and underwent periodic assessments of testicular function. Testosterone concentrations increased rapidly during treatment and all but one patient reached normal values. Testicular volume showed a sustained increase reaching almost 3-fold its baseline value. At the end of treatment, 48 patients (80.0%) had achieved a positive sperm count. The maximum sperm concentration during treatment was 24.5 +/- 8.1 x 10(6)/ml (mean +/- SEM). The median time to induce spermatogenesis was 5 months. Eleven patients reported adverse events, generally not related to treatment. Three patients experienced gynaecomastia. No local reactions at injection site were observed. In conclusion, the s.c. self-administration of highly purified FSH + HCG was well tolerated and effective in stimulating spermatogenesis and steroidogenesis in these patients.