We have developed a simple method for reconstructing a three-dimensional (3D) image in the operating room from sequentially scanned intraoperative two-dimensional (2D) power Doppler images using a personal computer and commercially available software. During three operations, 2 for cerebral aneurysm and 1 for cerebral tumor, intracranial vessel images were digitally transferred to a personal computer by freehand scanning over the dura mater or surface of the brain with a 7.5-MHz linear probe. A series of 2D images were converted to a smaller file, and 3D image was reconstructed with volume-rendering software. It took about 15 minutes to reconstruct of the initial 3D image. In the cases of cerebral aneurysm, the vessels connected to the lesion or running nearby were easily identified on the image. In the tumor case, the anatomical relation between the vascular structures and the tumor was clear. This simple 3D reconstruction method provides spatial information about intracranial vascular structures that is useful in intraoperative surgical planning.