Analyse outcome of FSH therapy alone after pituitary desensitization for assisted conception to compare with published results of conventional hMG. Descriptive study of complete series of patients undergoing IVF-ET or GIFT treatment using the chosen drug protocol without exception. University private IVF-ET clinic within a comprehensive fertility service. All couples (n = 773), including 10% > or = 40 years old, treated by IVF-ET or GIFT (1,097 cycles started and 1,012 attempted egg recoveries) for mainly tubal pelvic infective damage (36% of cycles), endometriosis (16%), sperm disorders (14%) and prolonged unexplained infertility (34%) during 3 calendar years, 1990 to 1992. Ovarian stimulation using FSH alone (urofollitropin, Metrodin; Serono Laboratories Limited, Welwyn Garden City, United Kingdom) after pituitary desensitization using buserelin acetate nasal spray (Suprefact; Hoechst, Hounslow, United Kingdom) from the previous midluteal phase, monitored by ultrasonography and serum E2 measurements, followed by standard IVF-ET or GIFT treatment methods limited to the transfer of no more than three embryos or eggs. Rates per cycle started of cancellation of egg recovery, failure of egg recovery, clinical pregnancy (ultrasound detection of sac), livebirths, and cumulative pregnancy rates (PR) and birth rates. In women < 40 years old and men with favorable sperm (77% of couples and 84% of cycles) the cycle cancellation rate of egg recovery was 7%; attempted egg recovery was successful in every case. For IVF-ET the clinical PR per started cycle and the livebirth rate were 27% and 23%, respectively, and for GIFT 39% and 33%, respectively. The four-cycle cumulative PR by either treatment was 77% and livebirth rate 68%. In women > 40 years old, the cycle PR and birth rate were 14% and 8%, respectively. In cases of sperm disorder the rates in women < 40 years old were 17% and 14%, respectively, and > 40 years old were 18% and 0, respectively. By comparison with the best worldwide results of assisted conception employing pituitary desensitization, the findings demonstrate that FSH alone to stimulate the ovaries is fully effective and highly successful, and supplementation with LH is not needed.