Multiple follicular development plays a major role in the successful outcome of IVF and embryo transfer treatment. Prediction of ovarian responses prior to stimulation is useful in counselling patients and helpful in tailoring the dosage of gonadotrophin to individual patients. The objective of this study was to compare age of women, body mass index (BMI), basal FSH concentration, volume of both ovaries and the number of antral follicles of both ovaries in predicting the number of oocytes obtained. A total of 128 consecutive women, who had no history of ovarian surgery, were non-smokers and undergoing the first cycle using a standard regimen of ovarian stimulation were examined. The total number of antral follicles achieved the best predictive value, followed by basal FSH, BMI and age of women. In those women with fewer antral follicles, a longer duration and higher dosage of human menopausal gonadotrophin were required but the number of eggs obtained was significantly less than for those with more antral follicles. Significantly more cycles were cancelled before egg collection in women with < or =6 antral follicles while more cycles of embryo transfer were postponed in order to reduce the risk of ovarian hyperstimulation syndrome in women with >9 antral follicles.