The aim of this study was to assess the ability of perfluoropropane-filled albumin microspheres to visualize tumor blood flow in woodchuck hepatomas. Ten tumors in five woodchucks with hepatomas were imaged before and after intravenous injection (dosages of 0.01 ml/kg to 2.0 ml/kg) of an agent using color Doppler sonography and gray scale ultrasonography. Both enhanced imaging modalities demonstrated blood flow around and within all tumors. Enhanced gray scale ultrasonography demonstrated sonographic "tumor blush" in seven tumors (70%). In conclusion, tumor blood flow in woodchucks was visualized more clearly using the agent on both color Doppler and gray scale ultrasonography.