This study was designed to evaluate the accuracy of a system to quantitate tumor vascularity with amplitude (power) color Doppler sonography two- and three-dimensionally. The vascularity of 20 transplanted murine tumors was determined with quantitated amplitude color Doppler sonography both two- and three-dimensionally and compared to tumor vascularity estimated by histologic examination. Serial examinations were performed 15, 30, 45, and 60 min after the injection of the exotoxin CM-101 and saline solution to assess changes in tumor vascularity. Three-dimensional amplitude color Doppler sonography best depicted the overall vascularity of tumor when compared to histologic estimation of vessel density. However, neither two- nor three-dimensional amplitude color power angiography correlated well to the microvessel count, probably a reflection of the difference in the method for vessel quantification using sonographic versus histologic techniques. Three-dimensional amplitude Doppler sonography correlated better with counts of large vessels (> 100 microm) as opposed to small vessels (> 15 microm). Time-activity curves showed no difference in tumor flow at the times measured in the experimental group injected with CM-101 or when compared to saline solutions in either the peripheral or central portions of the tumor. This three-dimensional amplitude color Doppler sonographic system affords global quantification of tumor vascularity and flow that may, in turn, be useful in determining the probability of malignancy (by determination of branching patterns and vessel regularity) or tumor response or both to treatment.