The most probable etiology of abnormal uterine bleeding relates to the patient's reproductive age, as does the likelihood of serious endometrial pathology. The specific diagnostic approach depends on whether the patient is premenopausal, perimenopausal or postmenopausal. In premenopausal women with normal findings on physical examination, the most likely diagnosis is dysfunctional uterine bleeding (DUB) secondary to anovulation, and the diagnostic investigation is targeted at identifying the etiology of anovulation. In perimenopausal patients, endometrial biopsy and other methods of detecting endometrial hyperplasia or carcinoma must be considered early in the investigation. Uterine pathology, particularly endometrial carcinoma, is common in postmenopausal women with abnormal uterine bleeding. Thus, in this age group, endometrial biopsy or transvaginal ultrasonography is included in the initial investigation. Premenopausal women with DUB may respond to oral contraceptives, cyclic medroxyprogesterone therapy or cyclic clomiphene. Perimenopausal women may also be treated with low-dose oral contraceptives or medroxyprogesterone. Erratic bleeding during hormone replacement therapy in postmenopausal women with no demonstrable pathology may respond to manipulation of the hormone regimen.