To evaluate the tumor blood flow in hepatocellular carcinoma, we have introduced color Doppler imaging during operation. 37 hepatocellular carcinoma patient with 54 nodules were included in this study. Following categories were analyzed, those were detectability of pulsatile blood flow and continuous blood flow signal in the tumor, pulsatile blood flow velocity depend on tumor size and pathological feature. Even the size of the tumor is less than 1 cm in diameter in 70% of those nodules we could detect and analyze the flow signal. This new modality could have a possibility to be a useful diagnostic device for small mass lesions in the liver.