The computed tomographic (CT) examinations of 17 patients undergoing evaluation for limb-sparing treatment of osteosarcoma were evaluated. In all cases information from CT directly affected the operative approach. The CT findings that helped in planning the operative approach included determination of intramedullary extent and evidence of 'skip' metastases, direct extension into an adjacent joint, and neurovascular compromise. Performing CT of the affected bone at 1-cm intervals from the joint above through the joint below and including the contralateral side in the field of view allow precise localization of findings that can direct the operative approach. Close and contiguous scanning intervals allow identification of small intramedullary 'skip' metastases that affect the resection margins.