The availability of pulsed Doppler probes has made it possible to sample signals at a chosen depth and thus to detect the flow in any selected deep vessel. Pulsed Doppler signal processing combined with real-time imaging, the so-called "duplex" method, is now also available for transvaginal transducers. The advantage of endosonographic ultrasound investigation is the possibility of using higher frequencies leading to a better resolution of anatomical structures of the small pelvis. Therefore this method allows the precise localisation of a deep vessel and the positioning of the Doppler sample volume within it. The transvaginal approach enables one to position the transducer close to the artery for better measurements. For our study we used a vaginal probe with 7.5 MHz with a pulsed Doppler equipment linked to a Combison 320 (Kretztechnik, Zipf, Austria). The integrated pulsed Doppler is not attached at a fixed angle but can be moved in the whole sector of 240 degrees. We investigated, if during follicle phase of the cycle changes of the pelvic blood flow velocity could be observed. 14 patients undergoing in vitro fertilization for sterility reasons participated in our study. We performed daily measurements of the blood-flow velocity of the ovarian artery and the internal iliac artery from cycle day 8 until the day of induction of ovulation. During cycle stimulation the observed decrease of the A/B ratio was dependent on cycle day and number of follicles. We found a decrease of the A/B ratio in the ovarian artery from 3.85 in cases with 2 follicles to 2.71 in cases with 5 follicles.(ABSTRACT TRUNCATED AT 250 WORDS)