PURPOSE: The aim of this study was to establish functional computed tomography (CT) imaging as a method for assessing tumor-induced angiogenesis. MATERIALS AND METHODS: Functional CT imaging was mathematically analyzed for 14 renal cell carcinomas by means of two-compartment modeling using a computer-discretization approach. The model incorporated diffusible kinetics of contrast medium including leakage from the capillary to the extravascular compartment and back-flux to the capillary compartment. The correlations between functional CT parameters [relative blood volume (rbv), permeability 1 (Pm1), and permeability 2 (Pm2)] and histopathological markers of angiogenesis [microvessel density (MVD) and vascular endothelial growth factor (VEGF)] were statistically analyzed. RESULTS: The modeling was successfully performed, showing similarity between the mathematically simulated curve and the measured time-density curve. There were significant linear correlations between MVD grade and Pm1 (r = 0.841, P = 0.001) and between VEGF grade and Pm2 (r = 0.804, P = 0.005) by Pearson's correlation coefficient. CONCLUSION: This method may be a useful tool for the assessment of tumor-induced angiogenesis.