The effect of exogenous human biosynthetic growth hormone (HGH; 12 IU/day; Norditropin, Novo-Nordisk) on the response to ovarian stimulation using a buserelin/human menopausal gonadotrophin (HMG) regimen was assessed in women who had previously shown a 'poor response' in spite of increasing doses of HMG. Forty patients were recruited into a prospective double-blind placebo-controlled study. The serum follicle stimulating hormone (FSH) on day 2-5 of a menstrual cycle (< 10 IU/l) was used to exclude any peri-menopausal candidates. The urinary 24 h GH secretion was normal in all patients. Thirty-three patients completed the study with 21 patients having human chorionic gonadotrophin (HCG) in both arms, thus providing a complete set of placebo control data. Of these 21 patients, the administration of HGH compared to the placebo cycle resulted in increased serum concentrations of fasting insulin on the 8th (median 3.9 versus 5.8 mU/l; P < 0.0005) and 13th (median 4.4 versus 5.8 mU/l; P < 0.05) day of HMG in those cycles receiving HGH. After 8 days of co-treatment with HGH the number of cohort follicles (14-16.9 mm) was significantly increased, but this change was not sustained on the day of HCG administration. No statistical difference in the serum oestradiol on the 8th day of HMG or day of HCG, length of the follicular phase, total dose of HMG used, or the number of oocytes collected was seen between the placebo or HGH cycles. This study demonstrates that HGH does not improve the ovarian response to ovulation induction in previous poor responders.