Intraoperative ultrasonography is a handy. real-time and cost-effective method for evaluation of tumors. We have examined 53 brain tumors during surgery using power Doppler ultrasonography (7.5-MHz sector scanner. ALOKA)with a contrast agent (Levovist^®). Blood flows inside and around the tumor are clearly visualized with power Doppler mode. By increasing the flow signals. a contrast agent is useful for evaluating the vascularity of a tumor and the location of surrounding vessels. The grade of flow signals in a tumor was well correlated with the vascularity assessed with digital subtraction angiography (p = 0.0004). Therefore, intraoperative power Doppler ultrasonography with a contrast agent provides informative data for safe and accurate surgery. especially in cases of hypervascular tumor such as hemangioblastoma. In conclusion. intraoperative power Doppler ultrasonography is useful for resection of tumors. If used in combination with navigation systems. ultrasonography can be replaced by inlraoperative angiography and MRI.