One-hundred women undergoing ovarian stimulation with gonadotrophin-releasing hormone agonist (GnRH-a) and a human menopausal gonadotrophin (HMG) for in-vitro fertilization (IVF) participated in this randomized comparative study. The effectiveness of long-acting s.c. goserelin (Zoladex depot; 49 patients) and intranasally (i.n.) administered buserelin acetate (Suprefact; 51 patients) for pituitary down-regulation was compared. Treatment with s.c. goserelin (3.6 mg) or i.n. buserelin acetate (200 micrograms; 6 times/day) was started on day 21-23 of the cycle. Stimulation with 150 IU of HMG/day was started after at least 11 days of GnRH-a treatment. There were no differences in the time required for follicular development nor in the clinical outcome between groups treated with either goserelin or buserelin. The number of oocytes recovered in the goserelin group was 6.7 +/- 5.0 versus 6.3 +/- 4.9 in the buserelin group. There were 11 pregnancies after the use of goserelin (22.4%) and 12 pregnancies in those given buserelin (24.0%). The number of HMG ampoules needed for follicular maturation was higher in the goserelin group (27.9 +/- 7.8) than in the buserelin group (24.6 +/- 7.8, P