Purpose : To determine the usefulness of microbubble contrast enhanced power Doppler ultrasonography (PDUS)for the detection of residual tumor in hepatocellular carcinomas (HCCs) treated by transcatheter arterialchemoembolization (TACE). Materials and Methods : Fourteen nodular HCCs (size range: 1 - 7.3 cm, mean: 3.5) intwelve patients treated by TACE, and on the basis of follow-up liver CT, thought to have a residual tumor, wereincluded in this study. Between July 1997 and April 1998, PDUS examinations were performed with a 2-4 MHz convextransducer before and after intravenous injection of a microbubble contrast agent (Levovist(, Schering AG, Berlin,Germany). Real-time power Doppler ultrasonographic images were recorded on videotape and representative imageswere color-printed. Tumor vascularity was analyzed on real-time images with regard to its presence or absence, andchanges, and two observers reached a consensus. The results were compared with those of other diagnostic tests(three-phase helical CT, conventional angiography, percutaneous biopsy, and/or surgical pathology). Results :Contrast-enhanced PDUS revealed intratumoral vascularity in ten of 14 tumors, none of which showed vascularity onunenhanced PDUS. In the remaining four tumors, both unenhanced and enhanced PDUS showed intratumoral tumorvascularity, which in all cases was more pronounced on enhanced than on unenhanced PDUS. Other diagnostic testsrevealed residual tumors in eleven lesions. Conclusion : Microbubble contrast-enhanced PDUS was more sensitivethan non-enhanced PDUS in depicting vascularity within a residual tumor and could be a useful method for thedetection of residual tumor in HCCs treated by TACE.