A total of 512 male rats were used to investigate the effects of H2-receptor antagonists on the liver after two-thirds hepatectomy or after carbon tetrachloride (CCl4)-induced hepatic injury. The serum aminotransferase levels in hepatectomy rats were significantly elevated as compared with those of rats with the sham operation 1 and 2 days after the operation. However, there were no differences in the serum aminotransferase levels and liver regeneration rates among the groups of hepatectomy rats who were treated with saline, cimetidine, or ranitidine. The injections of cimetidine or ranitidine did not induce a significant increase in serum amino-transferase levels or increase the severity of liver cell necrosis in CCl4-treated rats, as compared with the CCl4-treated rats who received saline injection. Thus, our data indicate that H2-receptor antagonists do not inhibit liver regeneration in rats after two-thirds hepatectomy or exert a detrimental effect on the liver cell necrosis in rats after CCl4-induced hepatic injury.