Ovarian hyperstimulation syndrome (OHSS) and multiple pregnancies are the two main complications of ovulation induction using gonadotropins. Withholding an ovulatory dose of human chorionic gonadotropin (hCG) remains the safest option for prevention of both complications. However, this policy frustrates both patient and physician, wastes time and money due to cancelled treatment, and results in cancellation of a high proportion of cycles that would not have progressed to clinical OHSS. As gonadotropin releasing hormone analogs (GnRH-a) may elicit surges of endogenous luteinizing hormone and follicle stimulating hormone, we investigated the usefullness of a single s.c. injection of leuprolide acetate (0.5 mg) to trigger ovulation, without inducing OHSS or multiple pregnancy, in 23 consecutive gonadotropin-stimulated cycles which would otherwise have been cancelled. All patients had at least 4 mature follicles (> or = 14 mm in diameter) and plasma estradiol levels > 1000 pg/ml on the day of GnRH-a injection. No luteal support was given. Seventeen of the 23 (74%) cycles were ovulatory and four singleton pregnancies resulted, giving a pregnancy rate of 17.4% per cycle. The remaining six patients (26%) clearly had defective or short luteal phases. No patient developed OHSS. It is concluded that GnRH-a may be an acceptable substitute for hCG to salvage treatment cycles in patients thought to be at risk for OHSS or multiple pregnancy. However, further studies are necessary for optimization of this approach in order to improve ovulatory and conceptional results.