PURPOSE: To characterize the ultrasonographic findings of polypoid adenomyoma of the uterus. MATERIALS AND METHODS: Ultrasonographic findings of twenty seven patients with histologically confirmed polypoid adenomyoma were retrospectively reviewed. Ultrasonography (US) was performed in all patients while sonohysterography (SH) in fifteen patients and color Doppler sonography (CDS) in thirteen patients were additionally performed. Location, size, growth pattern, surface, margin from the endometrium and underlying myometrium, echogenecity and echotexture, presence and patterns of cystic areas, hemorrhage, and posterior shadowing of the endometrial or submucosal mass on US and SH were evaluated. The presence of blood flow and resistive index (RI) on CDS were also evaluated. RESULTS: On US and SH, the tumor location was the corpus in sixteen cases, fundus in eight, and isthmus in three cases, and the tumor size ranged from 0.5 to 6 cm (mean 3.5 cm). The tumors were polypoid in eighteen cases, sessile in four cases, and pedunculated in five cases, and three of them protruded into the endocervical canal while two cases prolapsed through the external os. The surface was smooth in twenty six cases, lobulated in four and irregular in one. Nineteen cases had ill defined margin while eight cases, a well circumscribed margin. The mass was inhomogeneously isoechoic in twelve cases, homogeneously isoechoic in seven cases, homogeneously and inhomogeneously hyperechoic in four cases each, respectively. Cystic areas were seen in twenty cases, and there were three patterns of cystic areas: all solid mass (pattern 1, n=7), solid mass with cystic areas (pattern 2, n=18) and predominently cystic mass (pattern 3, n=2). Eight cases had hemorrhage and seven had posterior shadowing. CDS showed a blood flow with range of RI from 0.19 to 0.74 (mean 0.47). Other findings included adenomyosis in sixteen cases, leiomyoma in three, and endometrial thickening and mass in one each, respectively. CONCLUSION: Polypoid adenomyoma can be characterized as a heterogeneously isoechoic polypoid or pedunculated mass with multiple small cysts, hemorrhage, posterior shadowing and associated adenomyosis on US and SH. US could be useful in differentiating polypoid adenomyoma from other uterine polypoid tumors.