Intraobserver variation in transvaginal color Doppler ultrasound measurements in ovarian tumors was evaluated in 20 women selected from a group of patients undergoing surgical exploration for an ovarian lesion. Only those cases who were suspected of having a benign ovarian tumor other than a unilocular simple cyst were recruited. Pulsatility index (PI), resistance index (RI), peak systolic velocity (PSV) and time-averaged maximum velocity (TAMXV) were measured from intratumoral arteries in two repeat ultrasound sessions by the same observer. In each session, only two vessels with optimum Doppler signals were investigated. The repeatability of the measurements was studied by calculation of the within-subjects standard deviation (SD), the value below which the difference between the repeat measurements will lie with a probability of 0.95, the coefficient of variation (CV) and the intraclass correlation coefficient (intra-CC). The CV was 15% for the PI, 13% for the RI, 17% for the PSV and 23% for the TAMXV when the average value from two vessels was used. The corresponding intra-CC values were 0.86, 0.83, 0.96 and 0.90, respectively. In contrast, when a lowest (PI or RI) or a highest (PSV or TAMXV) value was preferred, the CV increased to 25% for the PI, to 18% for the RI, to 28% for the PSV and to 33% for the TAMXV. Similarly, the intra-CC values decreased. All in all, the averaged PI and RI measurements in intratumoral arteries were considered to be reliable. Averaged PSV and TAMXV measurements had high CV figures, raising some doubt as to the consistency of these variables. Averaged index values were more consistent than the extreme (lowest or highest) values.