A review of 118 treatment cycles in 115 women under prolonged GnRH analogue (GnRHa; leuprolide) treatment is presented. Patients were selected for treatment primarily on the grounds of poor previous response to stimulation (n = 40), advanced age (greater than 35 years; n = 29), previous premature luteinizing hormone (LH) surge (n = 30), polycystic ovarian disease (PCO; n = 12), and elevated androgens without evidence of PCO (n = 5). An overall pregnancy rate of 28.8% per treatment cycle was attained, compared with a pregnancy rate of 6.2% (6/97, of which none went to term) in the previous completed treatment cycle for the same patients. Ovarian response, as measured by oocytes recovered and maximum estradiol levels observed, was significantly improved in all groups and this was associated with a prolonged follicular phase, significantly more human menopausal gonadotropin (hMG) stimulation and a relatively high incidence of ovarian hyperstimulation, particularly in pregnant patients. Of specific techniques in the GnRHa cycle, GIFT produced a pregnancy rate per treatment of 50% (10/20); IVF-ET, 22% (8/36); PROST, 28% (13/46); and TEST, 19% (3/16). No cycles were abandoned, compared with a cancellation rate of 24% in previous cycles without GnRHa. Patients with PCO performed particularly well on GnRHa management, with a pregnancy rate per treatment of 58% (7/12). Pregnancy rates per treatment for the other groups were as follows: elevated age, 27% (9/33), high androgens, 40% (2/5); premature LH surges, 32% (9/28); and poor responders, 17.5% (7/40).(ABSTRACT TRUNCATED AT 250 WORDS)