The aim of this study was to assess the clinical usefulness of sonographic endometrium thickness measurement in asymptomatic postmenopausal women with endometrial fluid collection. Fifty-two asymptomatic postmenopausal women with endometrial fluid, who underwent endometrial sampling were evaluated. Histopathological findings revealed that 25 (48.1%) women had insufficient tissue, 20 (38.4%) had atrophic endometrium and 7 (13.5%) had endometrial polyps. No case of malignancy was found. There was no statistically significant difference between the various histopathological categories (insufficient tissue, atrophic endometrium and polyp) with regard to the mean single-layer endometrial thickness (1.54 ± 0.87, 2.04 ± 1.76 and 1.79 ± 0.69 mm, respectively, p = 0.436). Out of 44 patients with endometrial thickness of less than 3 mm, 38 (86.4%) had atrophic changes or insufficient tissue and 6 (13.6%) had endometrial polyps. In conclusion, if the endometrial thickness is 3 mm or less, endometrial sampling is not necessary in asymptomatic postmenopausal women with endometrial fluid.