A computer program was developed to assess the endometrial echogenicity relative to the myometrial one, based on the gray-level processing of the midsagittal uterine image. The endometrial region of interest was specified within the upper part of the uterine cavity. The adjacent area of the myometrium was used to determine the reference brightness. The endometrial region of interest was analyzed along the anteroposterior uterine axis, as a set of thin strips directed parallelly to the midcavitary line. The endometrial/myometrial relative echogenicity coefficient (E/M REC) was computed for each strip and displayed graphically as a function of the distance from the midcavitary line. The area under the E/M REC curve within the limits of the total endometrial width was defined as total area (TA) and was used as a measure of the endometrial echogenicity. This parameter was assessed in 9 patients during their normal ovulatory cycles and in 29 IVF-treated patients with mechanical infertility. TA has a significant linear increase during the days of the ovulatory cycles. TA was found in high correlation with log(estradiol). TA can be used reliably for sonographic endometrial dating in ovulatory cycles.