PURPOSE: To evaluate the efficacy of percutaneous microwave coagulation therapy (PMCT) combined with transcatheter arterial chemoembolization (TACE) for the treatment of hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Twenty-five nodular HCCs [long diameter of 1.2 -10 (mean, 3.4) cm] in 19 patients (15males and 4 females) were treated by PMCT 4-138 days after TACE. Under ultrasound guidance, the carcinomas were punctured with a 14-G guideneedle through which a microwave electrode(25.0 cm in length, 1.6mm in diameter) was inserted. To coagulate the HCCs and surrounding hepatic parenchyma, microwave irradiation at 60W for 45 -60 seconds was then applied. One to three sessions of PMCT were performed at intervals of 2-6 days, and one week to 29 months later, the therapeutic effect was evaluated by spiral CT, angiography, and serum alpha-fetoprotein. RESULTS: Eighteen of 25 HCCs (72.0%) were necrotized completely, but seven (28.0%) recurred. Ninety percent of HCCs smaller than 4 cm in long diameter showed complete remission, but all those larger than 4 cm recurred. Alpha-fetoprotein levels decreased markedly in five patients (26.3%), while in 12 (63.2%), asparate aminotransferase (AST)/alanine aminotransferase (ALT) showed transient elevation. Minor complications occurred after PMCT (mild abdominal pain in 8 patients, fever in 7, pleural effusion in 3, portal vein thrombosis in 1, and hepatic abscess in 1), but in no case was this serious. CONCLUSION: PMCT combined with TACE provides effective and safe treatement for nodular HCCs with a long diameter of less than 4 cm.