The efficacy of combined growth hormone (GH)-gonadotropin treatment has been studied in patients previously resistant to sole gonadotropins for induction of superovulation. Eleven patients (aged 26-41) with a mechanical cause of infertility were treated. All were given the same dosage of gonadotropins as in previous cancelled cycles (6-17 ampules/cycle of menofollitropin; 34-80 ampules/cycle of human menopausal gonadotropin) plus a standard dosage of GH (0.1 IU per kg body weight, daily). Younger patients (n = 6, age 26-36) showed a considerable improvement of ovarian response in terms of number of mature follicles aspirated by laparoscopy (performed on day 11-13). Older patients (n = 5, age 39-41) did not show any significant improvement of ovarian response with combined treatment and all had their stimulatory cycle cancelled. Follicular fluid (FF) levels of GH, 17 beta-estradiol (E2) and progesterone (P) were significantly higher in the group of younger GH-treated patients (n = 53 follicles) than in 4 controls treated with gonadotropins only (n = 32 follicles). FF insulin-like growth factor-I (IGF-I) did not significantly differ between the two groups. A significant positive linear correlation has been found between FF GH and IGF-I in the GH-treated group. In conclusion, GH-gonadotropin combined treatment considerably improves ovarian response in protocols for superovulation induction in younger gonadotropin-resistant patients. A local action of GH and IGF-I in the ovaries may be hypothesized.