A patient who suffered from polycystic ovarian disease and anovulation, was treated with pure follicle stimulating hormone for induction of ovulation. The treatment was stopped and human chorionic gonadotrophin was not administered because of high serum oestradiol levels and multiple follicular development. Ovulation occurred 11 days after pure follicle stimulating hormone was discontinued, the patient developed third-degree ovarian hyperstimulation syndrome and conceived with a quintuplet pregnancy.