Uterine myoma and adenomyosis are the two most likely diagnoses in women with hypermenorrhea, dysmenorrhea, and an enlarged uterus, but it is often not possible to make a distinction between them preoperatively. But their treatments can differ: myoma can be treated through myomectomy whereas adenomyosis requires hysterectomy. In order to establish the characteristic and differential findings of myoma and adenomyosis sonographically, sonographic findings of 125 cases of pathologically proven myoma and adenomyosis were reviewed retrospectively. Histologic diagnoses were myoma in 94 patients and adenomyosis in 31 patients. The results were as follows 1. The common sonographic findings of uterine myoma were globular enlargement or bulging contour of uterus 77.8%, loss of central endometrial echoes 66.0%, and homogeneous decreased internal echoes 35.1% or heterogeneous internal. echoes 44.7%. 2. The common sonographic findings of adenomyosis were diffuse enlargement without contour change 80.6%, homogeneous hypoechoic or isoechoic internal textures 96.8%, preserved central endometrial echoes 80.6%, and thickening of posterior uterine wall 64.5%. 3. Adenomyosis was highly suggested if the uterus showed diffuse enlargement without contour change or visible nodule, homogeneous hypoechoic textures, and especially thickened posterior wall with anteriorly displaced central endometrial echoes. 4. Adenomyosis could be excluded if the patient was under 30 or above 50 years old, and especially had no previous obstetric history.