Twelve cases of hepatocellular carcinoma treated by arterial embolization were followed with ultrasonography. Shrinkage of the tumor after the therapy was confirmed in all cases. Echo level reduction in the tumor occurred in 10 cases. High-level reverberation echoes with acoustic shadows emerged in seven cases; however, these echoes were not detected in any cases 3 weeks after the procedure. Echoes were considered either as the consequence of gas produced in the tumor or air trapped in the embolic substance. Ultrasonography, therefore, is an effective technique for the posttherapeutic evaluation of arterial embolization therapy for hepatocellular carcinoma.