Microwave coagulo-necrotic therapy (MCN) was performed in 21 patients with small hepatocellular carcinoma less than 5cm in diameter and this therapeutic method was determined to be effective from the following results. 1) A marked low density area was seen in the region receiving the therapy and no enhanced findings were observed by enhanced CT one month postoperatively. 2) Recurrence appeared in 5 patients (23.8%) and only one patient died 1 year and 6 months after the operation. However, the other 20 patients survived for a maximum of 3 years and 2 months postoperatively. 3) The levels of total bilirubin and GOT in these patients were similar to those of patients who underwent hepatectomy. However, the levels of prothrombin time and hepaplatin test in patients with MCN changed less than in those who received hepatectomy. 4) Tendency of the renal failure was seen in 2 patients, and the other 19 patients did not have any complication postoperatively.