A prospective pilot study was conducted to evaluate the usefulness of uterine artery blood flow in the detection of various pathologic endometrial conditions in 39 asymptomatic postmenopausal breast cancer patients who were treated with tamoxifen. No specific pattern was seen for the uterine artery pulsatility index values in the tamoxifen-treated patients that could be related to any specific endometrial lesions, nor were any specific changes observed in the pulsatility index value with increasing severity of the pathologic endometrial conditions. Similarly, no correlation was found between ultrasonographically measured endometrial widths and uterine artery pulsatility index values. Thus, although pulsed Doppler flow ultrasonography has been shown previously to be effective in the detection of uterine cancer in non-tamoxifen-treated post-menopausal patients, it probably does not contribute to the assessment of endometrial lesions in post-menopausal breast cancer patients treated with tamoxifen.