Eleven children in whom a retroperitoneal neuroblastoma was suspected on the basis of plain radiographic or urographic findings underwent computed tomography (CT). CT identified and localized a neurogenic tumor in eight patients. Calcifications were demonstrated by CT in six lesions, but by urography in only four. One neuroblastoma detected by CT was not seen on the urogram; in five patients greater extent of the tumor was defined by CT than by conventional radiologic procedures. In three patients CT excluded a neuroblastoma, but diagnosed other disorders (hepatic tumor, pancreatitis, and retrocaval ureter). Our results confirm that CT is a simple and accurate method for diagnosis, delineation of extent, or exclusion of neuroblastoma.