Between November 1973 and December 1996, the in situ freezing of tumor, i.e., cryotherapy, was performed with liquid nitrogen (-196 degrees C) on 235 patients with primary liver cancer (PLC). There were no operative mortalities or severe complications. The 5-year survival was 39.8% for the 235 PLC patients, and 55.4% for the 80 patients with small PLC (< or = 5 cm). When analyzed with respect to treatment modalities without considering the size of the tumor, the 5-year survival was 26.9% for 78 PLC patients treated by cryotherapy alone; 39.6% for 58 PLC patients treated by cryotherapy plus hepatic artery ligation and perfusion; 46.0% for 27 PLC patients treated by cryotherapy for residual tumor plus resection of the main tumor; and 60.4% for 72 PLC patients treated by cryotherapy followed by resection of the frozen tumor. These results indicate that cryotherapy is a safe and effective treatment for PLC.