Objective. To examine the diagnostic feasibility of sonographic gray scale histograms to assess changes in the endometrium following abortion induced by mifepristone and misoprostol. Design. Retrospective study. Setting. Taipei Medical University-Wan Fang academic medical center. Population or sample. A total of 109 patients who matched eligibility criteria were divided into three groups: (a) complete abortion, (b) normal menstrual cycles, and (c) incomplete abortion. Methods. Ultrasonographic examination of the uterus with fixed settings on each patient and sonographic gray scale histograms with image analysis software, using multivariate analysis by the partial least square model. Main outcome measures. Thickness, brightness, area and distribution of pixels of the endometrium and its contents. Results. The groups could be discriminated (p <0.01, KruskalWallis test) using the analyzed gray scale histograms. The classification between complete and incomplete abortion reached 97% sensitivity and 100% specificity. Conclusions. Partial least square analysis of gray scale histograms of the endometrium in ultrasonographic images is useful in assessing endometrial changes.