Seven patients with polycystic ovarian disease (PCO) and having polyfollicular development following ovulation induction by human menopausal gonadotrophin underwent selective follicular reduction by transvaginal ultrasound-guided aspiration of all follicles greater than or equal to 10 mm in diameter leaving two or three preovulatory mature follicles. Twenty-four and 48 h after injection of human chorionic gonadotrophin, the couples had intercourse. Five patients achieved pregnancy in 15 treatment cycles, four in their first cycle after 14 previous unsuccessful stimulation cycles. Four have delivered healthy children: three singletons and one set of twins. One patient spontaneously aborted twins in week 22 of pregnancy. No major complications were encountered. Selective follicular reduction seems to be a possible approach to the treatment of PCO patients having polyfollicular development following ovulation induction.