OBJECTIVE The purpose of this study was to evaluate the possible effect of the antihypertensive agent nifedipine (a calcium channel antagonist) on the endometrium of asymptomatic menopausal women by using transvaginal sonography, hysteroscopy, and endometrial sampling. DESIGN Eighty-five asymptomatic postmenopausal women with an ultrasonographically detected endometrial thickness of more than 7 mm were examined. The study group comprised 43 women treated with nifedipine (30-60 mg/day) for mild to moderate hypertension for at least 1 year, and the control group comprised 42 normotensive women. All participants underwent transvaginal sonography, hysteroscopy, and, if necessary, endometrial biopsy. RESULTS Of the 85 patients, 53 were found to have atrophic endometrium, 36 (83.7%) in the study group and 17 (40.5%) in the control group. The difference between the groups was statistically significant (p < 0.05). There were three cases of hyperplasia and three cases of carcinoma of the endometrium, with similar rates in the two groups. CONCLUSIONS Among asymptomatic postmenopausal patients with sonographically thickened endometrium, atrophic endometrium was found to be significantly more prevalent in those using calcium channel antagonists to control hypertension than in those who were normotensive controls. The presence of endometrial hyperplasia and malignancy in the study group underscores the importance of meticulous endometrial evaluation whenever sonographically thickened endometrium is encountered.