Color Doppler sonographic findings on 38 lesions in 31 patients who had primary hepatocellular carcinoma were evaluated before and after transcatheter arterial embolization and compared with dynamic CT and hepatic arteriographic findings. All lesions that were observed with dynamic CT or arteriography were correctly identified on color Doppler sonography. Peritumoral pulsatile flow was the predominant color Doppler flow seen in all lesions. Mixed pulsatile and continuous flow were noted in larger tumors and in tumors with a higher degree of vascularity, as determined by arteriography. Two weeks after treatment, color Doppler flow was still identified in 18 lesions (47%), corresponding to dynamic CT or arteriographic findings documenting residual tumor. Histopathologic examination, performed in 10 other lesions, showed that the tumor was completely necrotic in five. These five necrotic tumors were not visible on color Doppler flow images after treatment. Viable tumor was observed in the five remaining lesions, all of which were shown on color Doppler flow images after treatment. During the 6- to 16-month follow-up period, color Doppler flow images showed recurrence of 13 (50%) of 26 lesions, corresponding to tumor recurrence as shown by CT and arteriography. We conclude that color Doppler sonography is useful for imaging hepatocellular carcinoma, for evaluating residual tumor after treatment, and for imaging tumor recurrence during follow-up.