Aim: To examine the usefulness of a gray scale histogram and computer assisted image analysis software in assessing physiologic states of the endometrium with ultrasonography. Methods: Seventy patients at the Taipei Medical University-Wan Fang Hospital who matched eligibility criteria were categorized into one of three groups: (i) normal menstrual cycle, (ii) postmenopausal, and (iii) post incomplete abortion. Ultrasonography of the uterus was performed on each patient and the endometrium was analyzed with ImageJ image analysis software. Results: A statistically significant difference in signal intensity scores of the gray level histogram, represented as m j, was found between the groups. Conclusion: Ultrasonographic images analyzed using computer assisted image analysis software and gray level histogram are useful in assessing the physiological state of the endometrium.