The aim of the study was to find out whether the estimation of the baseline ovarian volume prior to stimulation would be a suitable predictor for the risk of ovarian hyperstimulation syndrome (OHSS). A total of 101 patients underwent in-vitro fertilization (IVF) and embryo transfer. They had a 3-D volumetric assessment of the ovaries and body weight estimations on the first day of hormonal stimulation. A second measurement was performed on the day of ovulation induction with human chorionic gonadotrophin (HCG) together with an oestradiol 17 beta estimation in serum. During the IVF programme 15 women developed OHSS and 86 did not. There was a significant correlation between the baseline ovarian volume and subsequent occurrence of OHSS (P = 0.03). Other significant relationships were found between the occurrence of OHSS and the number of follicles (P = 0.002), the number of oocytes retrieved (P = 0.0001) and the length of the cycle (P = 0.0001). The body weight before and after the stimulation was significantly lower in the group of women who did develop the syndrome (P = 0.011 resp. 0.03). The oestradiol 17 beta concentration on the day of HCG administration in the serum of the patients who had OHSS was significantly higher (P = 0.0001). In conclusion, volumetry of the ovaries could help to detect patients at risk and prevent the occurrence of OHSS by early adjustment of the hormonal dosage. Recent advances in ultrasound technology (3-D ultrasound) enable quick and highly accurate volumetric assessments. Furthermore, our study confirms previous observations that low body weight and long cycles seem to be additional risk factors for the development of OHSS.