Ovarian hyperstimulation syndrome (OHSS) is a serious complication of ovulation induction. It is most often associated with the administration of human menopausal gonadotropins (hMG) or purified preparation of follicle stimulating hormone (FSH), but has also been reported after clomiphene (CC) and in patients with hydatiform mole and chorioepithelioma. Moreover, OHSS has been observed in cases of multiple pregnancy unrelated to the use of fertility drugs. In recent years, the hormonal induction of ovulation has been practised to an increasing degree, partly due to the extended use in vitro fertilization (IVF) and gamete intra fallopian transfer (GIFT) techniques in the treatment of infertility. This trend will undoubtedly result in a growing number of patients with OHSS: For this reason, it is important to elucidate the pathophysiological mechanisms responsible for trigging this condition and discuss the treatment possibilities once it has arisen. We will present three patients who developed OHSS after different attempts at ovulation induction. Interestingly, aspiration of the follicles, which was carried out in two of the cases, did not influence the progress of the condition.