To evaluate the clinical effect, CT image changes and side-effects of percutaneous microwave coagulation therapy for lung cancer.CT-guided percutaneous puncture was performed using a needle mono-pole microwave antenna with 65W, 2 450 MHz microwave delivered in 60 seconds to 20 peripheral lung cancer patients, including 8 suffering from primary lung cancer and 12 metastatic lung cancer (totally 28 lesions).Sixteen patients were alive after having been followed-up for 3 approximately 24 months. All patients showed nodules decreased in size. Diminution of over 50% was observed in 13 nodules and 3, completely disappeared. The overall response rate was 57.1%. Ellipsoid shadow 3.5 cm x 2.5 cm across was observed by CT in lesions immediately after coagulation. Gasification within the coagulated area was observed in a week with a high density in the peripheral region. Consolidation was observed in 3 months and the lesion disappeared 1 year later. Complete tumor necrosis was proved by biopsy. No side-effects or complications were observed.Percutaneous microwave coagulation therapy is a new safe treatment for lung cancer, giving marked effect but minimum trauma.