A retrospective analysis of ovarian hyperstimulation syndrome in high responders undergoing in-vitro fertilization (IVF) is presented. High responders were defined as having > 20 follicles and serum oestradiol > 3000 pg/ml after treatment with human menopausal gonadotrophin. Of the initial 30 IVF cycles in high responders, 23 developed a moderate-to-severe ovarian hyperstimulation syndrome (76.7%). Subsequently, 15 other IVF cycles in high responders were combined with a repeated aspiration of ovarian follicles and corpus luteum cysts just prior to embryo transfer. Only three patients (20%) developed a moderate ovarian hyperstimulation syndrome (P = 0.0004). We conclude that repeated follicular aspiration is safe and results in a significant reduction in the incidence and severity of this condition in high responders undergoing IVF.