The long-acting agonist analogue of LHRH, Buserelin (Hoechst) has been used to suppress endogenous gonadotrophins prior to induction of ovulation with low dose human menopausal gonadotrophin (HMG) in women with clomiphene-resistant polycystic ovary syndrome (PCOS). The results have been compared with those in a similar group of patients treated with HMG alone. Buserelin (900–1,500 µg/day) was given intranasally to 11 women who thereafter received a total of 33 cycles of treatment with low-dose HMG. The control group comprised 16 women who received 40 cycles of HMG without Buserelin pretreatment. The ovulation rate was similar in the two groups: Buserelin + HMG 70%, HMG alone 68% and both groups showed a high rate of single follicle ovulation (52 and 63%, respectively). The threshold dose of gonadotrophin required to induce a single follicle was similar in the two groups. Premature elevation of LH in the late follicular phase was common in women who received HMG alone, but did not occur in any cycle in the patients receiving Buserelin pretreatment. In summary, these data show that pretreatment with an LHRH analogue prevents a premature LH surge but it remains to be determined whether this will have a significant bearing on the rate of successful pregnancy in women with PCOS.