Objective: The aim of this study was to evaluate the feasibility and therapeutic effectiveness of ultrasonography (US)-guided percutaneous microwave ablation (PMA) in the treatment of peripheral lung cancer. Methods: From December 2002 to September 2003, 12 Chinese patients with 16 histologically proven lung malignant tumors (6 primary and 10 metastatic) were treated with US-guided PMA. All tumors were located at the peripheral portions of the lung where the tumors were in direct contact with visceral pleura and visualized on US. A total of 21 insertions with 25 applications was administered to the 16 tumors. There was no radiation or chemotherapy combined with PMA. Results: Based on the follow-up period of 6-40 months (average=20 months), seven patients survived without serious complications and five patients died from metastasis after PMA. The size of treated tumors was decreased in all cases (10 tumors with moderate to remarkable area reduction and 6 tumors with mild area reduction). Blood flow in the tumors became either invisible or diminished on color Doppler flow imaging, which showed 9 tumors with no enhancement and 7 tumors with partially decreased enhancement on contrast-enhanced computed tomography after PMA. All patients experienced improvement of clinical symptoms after PMA treatment. Conclusions: Ultrasonography-guided PMA, a mildly invasive procedure, is an effective, safe, and feasible method for treating peripheral lung tumors. Percutaneous microwave ablation provides an alternative therapy for patients with inoperable peripheral lung cancer as well as for patients who refuse radiation or chemotherapy. (C) 2006 Elsevier Inc. All rights reserved.