Ovarian hyperstimulation syndrome (OHSS) is the most serious, life-threatening, iatrogenic complication of ovulation induction. The importance of excessive oestradiol concentrations on the day of human chorionic gonadotrophin (HCG) administration as a predictor and factor in the pathophysiology of OHSS has been extensively studied and discussed. We present the case report of a woman with hypogonadotrophic hypogonadism who developed severe OHSS during ovulation induction with urinary human follicle stimulating hormone (FSH) and HCG in the presence of low circulating oestradiol concentrations. The implication of FSH treatment and complications in hypogonadotrophic hypogonadal patients, and the role of preovulatory oestradiol concentrations in the prediction of OHSS, are discussed.