Surgical resection is the cornerstone of curative therapy for primary and metastatic liver tumors. For best results, the surgeon must know the location of all hepatic tumor nodules relative to the major vessels that define the liver's surgical anatomy. Computed tomography is very sensitive for detecting liver tumors, but its planar slices do not fully address the three-dimensional nature of this surgical problem. We have developed a technique using volume rendering of computed tomography data that provides a preoperative 3D map of the liver showing tumor location relative to key blood vessels. This technique also has important implications for emerging, minimally invasive therapies.