PURPOSE: To evaluate the usefulness and limitations of power Doppler sonography in determining the tumor vascularity. MATERIALS AND METHODS: Power Doppler sonography was performed on VX2 carcinomas present in rabbit thighs, and the findings were compared with those of microangiography in an almost identical plane. Tumor vascularity was qualitatively analysed on the basis of tumor vessel distribution and density, and the presence of thick and thin vessels; for a comparison of tumor vascularity as seen on microangiography, tumor blood flow signals shown by power Doppler sonography were graded 3, 2, 1, 0. For quantitative analysis, a comparison was made of the percentage of signed-rank test and Spearman correlation test. RESULTS: Mean tumor vascularity scores, as seen on power Doppler sonography, and relating to tumor vessel distribution and density, and the presence of thick and thin vessels, were 2.87, 2.73, 2.93 and 2.73, respectively. The mean and medians of the percentages of tumor area occupied by vessels were 22.7% & 23.5% and 34.7% on microangiography and power Doppler sonography, respectively. Thus, there was good correlation between these two modes. CONCLUSION: Power doppler sonography could demonstrate the tumor vascularity on microangiography relatively well but tend to overestimate it.