Seven patients with lung tumors underwent percutaneous implantation of iodine-125 sources into the tumor. Needle placement and seed implantation were effected with biplane fluoroscopy and a computer planning model based on computed tomography. No complications were encountered. Five of the seven patients underwent the procedure at the outpatient center and were discharged the same day. Follow-up radiologic evaluations were available for six patients; in all six the examination demonstrated tumor shrinkage, and in four tumor shrinkage was essentially complete.