Adenomyosis has been referred to as diagnostically elusive due to the difficulty of clinical identification and unknown etiology. In a retrospective study of 178 consecutive uteri removed or biopsied at Howard University Hospital significant differences in the average age and peak incidence, correct preoperative diagnosis, and association with leiomyoma was noted when compared with the current literature. The data suggest that in black Americans symptomatic essential adenomyosis occurs earlier and that dilation and curettage may have an etiologic role. In general, adenomyosis is more frequently associated with leiomyoma but essential adenomyosis was diagnosed most consistently when uterine enlargement was noted during the menstrual period. The authors conclude that adenomyosis should be considered in all cases of abnormal uterine bleeding and dysmenorrhea. Early diagnosis by ultrasonographic testing may lead to an identifiable cause of this disease and result in methods of prevention or early medical therapy.