The role of transvaginal pulsed colour Doppler ultrasound in the prediction of the outcome of in-vitro fertilization (IVF) therapy was assessed longitudinally in 30 patients during stimulated cycles. The pulsatility index (PI) of the uterine arteries did not change significantly until the mid-luteal phase. Within 6 days after the beginning of stimulation the maximum peak systolic velocity of the uterine blood flow had increased significantly from 27.6 +/- 8.9 to 36 +/- 12.8 cm/s. No difference was found in uterine PI between pregnant and non-pregnant women. The PI of intra-ovarian flow was also similar in both groups. However, there was an insignificant increase in uterine receptivity when the PI of the uterine artery was between 2.0 and 2.99 on the day of embryo transfer. Nevertheless, the appraisal of the prognostic outcome of the treatment could not be made with Doppler.