This multicenter study was designed to determine if CT can assess operability in stage III neuroblastoma. Nineteen children (11 boys, eight girls), aged 2-51 months, considered to have, by conventional clinical and radiographic examinations, localized neuroblastoma that crossed the midline were examined by CT. After intravenous and oral contrast media enhancements, CT was able to show the relation of the tumor to the adjacent vital vessels: aorta, celiac axis, and superior mesenteric artery. In all 15 patients, tumors that encased the aorta or its major branches were unresectable. However, three of four tumors crossing the midline but not coming into contact with the aorta or adherent only to one side of the vessel could be resected. Because surgery currently plays the major role in the treatment of neuroblastoma, the relation of the tumor to the aorta and great vessels is a more reliable and important factor in predicting the outcome of these children than the extension and location of the tumor with reference to the midline. CT after intravenous contrast enhancement can establish this relation and assess resectability.