The outcome of in-vitro fertilization treatment using buserelin, an agonist of luteinizing hormone releasing hormone, given in a short stimulation regimen with human menopausal gonadotrophin (HMG), was compared with a conventional regimen including clomiphene citrate (CC). A total of 94 infertile women underwent cycles of treatment with intranasal buserelin, 500 micrograms daily from the first day of menstruation and also HMG daily from the third day. The same patients had previously undergone unsuccessful treatment cycles with CC and HMG. Overall, addition of buserelin resulted in fewer cycles being abandoned (10 versus 34%) and none of the patients ovulated prior to collection. The mean total dose of HMG required was increased by 74% in buserelin cycles. Significantly more oocytes were collected with buserelin treatment (mean 5.9 versus 4.4, P less than 0.01) and, thus, significantly more embryos were transferred (mean 2.3 versus 1.2, P less than 0.0001) although fertilization and cleavage rates were unchanged. Fifteen pregnancies were achieved, giving a clinical pregnancy rate of 22% per embryo transfer. These pregnancies resulted in 16 live births (7 singletons, 3 twins, 1 triplets). Four pregnancies failed before 14 weeks gestation. We conclude, therefore, that the substitution of buserelin for CC for ovarian stimulation in poor responders results in an improved outcome, both in terms of the number of oocytes collected and the pregnancy rate per treatment cycle.