Although most of hemangiomas of the liver are demonstrated as hyperechoic lesions by ultrasound, some hemangiomas are hypoechoic. To investigate the cause of hypoechoic pattern, we examined 30 hepatic hemangiomas in 25 patients by ultrasound and compared with the results of the angiography during the last 5 years. The pattern of the hemangioma was hypoechoic in 8, isoechoic in 1, and hyperechoic in 21. By ultrasound, posterior echo enhancement was observed in 5 (62%) of 8 hypoechoic lesions, 0 (0%) of 1 isoechoic lesion, and 4 (19%) of 21 hyperechoic lesions. The pooling findings of the angiography which revealed vascularity were classified into three grades: (+), (++), and (+++). In 8 hypoechoic lesions, 2 (25%) showed pooling (+), 1 (13%) pooling (++), and 5 (62%) pooling (+++), although none of 21 hyperechoic lesions showed pooling (+++). Hypoechoic pattern of hepatic hemangiomas by ultrasound seems to be consistent with the pooling (+++) by angiography. In conclusion, dilated vascular cavity of the hemangioma causes the hypoechoic pattern by ultrasound.