In order to evaluate possible benefits of local therapy of lung tumors--electrolysis at Pt-electrodes percutaneously inserted in the tumor, followed by radiation therapy--6 pigs were used as test objects. Two died of lung hemorrhage due to too fast electrolysis causing lung rupture but the other 4 survived when electrolysis was performed at a lower speed. No complication was observed of the combination of electrolysis and external beam irradiation. One human primary lung tumor was treated and probably destroyed by two electrolytic procedures and irradiation to 64 Gy. The evidence of the limited series of animal experiments and of single human tumor case would indicate that further investigations seem worthwhile.