A 12-month prospective study of 120 consecutive hysterectomy and 12 myomectomy specimens received at the histopathology laboratory of the Obafemi Awolowo University Teaching Hospitals was undertaken to determine the occurrence of adenomyosis. The observed incidence was 9.8%. Adenomyosis was commonest in multiparous women in the fifth decade of life. The principal presenting complaint was abnormal uterine bleeding. The average dimension of a typical affected uterus was 10 x 7 x 6 cm weighing an average of 175 g. Diagnosis was mostly post-operative. This study shows that adenomyosis uteri is not uncommon in Nigerians.