OBJECTIVE We determined whether or not self-administered subcutaneous human menopausal gonadotrophin (hMG) therapy is safe and effective in the stimulation of testicular growth and initiation of spermatogenesis in men with hypogonadotrophic hypogonadism where human chorionic gonadotrophin alone had failed. METHODS Human menopausal gonadotrophin was self-administered subcutaneously in two dosage regimens to patients requiring (a) fertility (Group I), 37.5 IU twice daily (total weekly dose 525 IU) (n = 7) and (b) increased testicular size (Group II) 37.5 IU once daily (total weekly dose 265.5 IU) (n = 2). Patients were assessed on a monthly basis. METHODS Nine patients with hypogonadotrophic hypogonadism were studied. Six patients had idiopathic isolated hypogonadotrophic hypogonadism, one Kallman's syndrome, one idiopathic isolated hypogonadotrophic hypogonadism secondary to trauma and one with panhypopituitarism secondary to radiotherapy for a hypothalamic pituitary tumour. Five of these patients had a history of unilateral or bilateral cryptorchidism. METHODS Semen analysis and serum testosterone. Testicular size was assessed by use of a Prader orchidometer. RESULTS Six of seven patients (four with a history of cryptorchidism) requesting fertility attained sperm counts of > 10 million/ml. Three pregnancies have been achieved so far. One failure occurred in a patient with a previous history of cryptorchidism. In Group I patients (a) with an initial testicular volume of 4 ml or less (n = 4), mean size increased from 3.25 +/- 0.9 (SD) ml to 12.2 +/- 3.8 ml, (b) an initial testicular volume of > 4 ml mean size (n = 3) increased from 9.2 +/- 3.9 ml to 10.3 +/- 4 ml. In Group II (n = 2) testis size increased from a mean of 3.0 +/- 1.4 ml to 9.0 +/- 1.4 ml over a 6-months treatment period. CONCLUSIONS Self-administered subcutaneous human menopausal gonadotrophin is a safe and effective mode of therapy in increasing testicular size and inducing spermatogenesis in males with hypogonadotrophic hypogonadism.