PURPOSE: To assess the value of contrast-enhanced color Doppler ultrasonography(US) in the detection of ves-sels related to hepatocellular carcinoma(HCC). MATERIALS AND METHODS: Between July 1997 and April 2000, 76 HCCs in 70 patients (50 men and 20 women; mean age, 57.8 years) were confirmed histologically or clinically. Tumor site and size at gray scale US, and afferent, intratumoral and efferent color signals at precontrast and postcontrast color Doppler US were deter-mined. Afferent signals were classified as basket or penetrating type, and intratumoral signals as spotty, linear or mixed. Efferent signals were categorized as signal to portal vein or signal to hepatic vein, and postcontrast color signal changes as focal, general or marginal spotty type. We also measured the color percentage of intra-tumoral signals as seen during precontrast and postcontrast study. RESULTS: The detection rate changed from 41(53.9%) to 60(78.9%) in cases with afferent signals, from 50(65.8%) to 64(84.2%) in those with intratumoral signals, and from 6(7.9%) to 9(11.8%) in those with efferent signals. Overall, 74(97.4%) cases showed positive findings at postcontrast color Doppler US. The most common enhancing pattern was general, occurring in 33(43.4%) cases. The color percentage of intratumoral signals increased from an average of 8.2% to 34.9%. The detection rate of intratumoral signals from tumors less than 3 cm in diameter increased from 56.8% to 100%, and that of deeply-located tumor-related signals (17 cas-es) increased from 47.1% to 94.1%. CONCLUSION: The use of contrast enhanced color Doppler US increased the detection rate of afferent, intratumoral, and efferent signals, especially that of intratumoral signals from tumors less than 3 cm in diameter and signals from deeply located tumors. In addition, the modality can aid the diagnosis of HCC by evaluating tumor dynamics.