Objective To assess the effect on spermatogenesis of adding recombinant follicle-stimulating hormone (FSH) to human chorionic gonadotropin (hCG) treatment protocols for adolescent/young adult males with hypogonadotropic hypogonadism (HH). Design Observational descriptive study. Setting Outpatient clinics. Patient(s) Nineteen males with hypogonadotropic hypogonadism, aged 14.5 to 31.0 years. Intervention(s) Treatment with either hCG treatment alone (n = 9; group 1) or in combination with recombinant FSH (n = 10; group 2), over 6 to 9 months. Main Outcome Measure(s) Combined testicular volume (CTV) and testosterone, inhibin B, semen/urine analysis at 6 to 9 months. Result(s) There were no differences between the two groups in baseline variables or changes in CTV with treatment. Despite this, evidence of spermatogenesis was present in all group 2 patients by 9 months (range 0.2 to 15 × 106 /mL) compared with three of nine patients in group 1 (range 0 to <1 × 106 /mL). Whole group and subgroup analyses did not demonstrate any statistically significant correlations between age at onset of treatment and either CTV or sperm count. Conclusion(s) The addition of recombinant FSH to hCG treatment protocols in adolescent/young adult HH males results in normal testicular growth and may hasten induction of spermatogenesis.