Objectives : This study was designed to investigate the effect of Injinsammul-tang (IJS) on hepatocellular carcinogenesis in rats. Methods : Sprague Dawley (SD) rats of control and treatment groups received intraperitoneal injection of 50 mg/kg/day diethylnitrosamine (DENA) weekly for 8 weeks. Experimental rats were classified into 3 groups; normal group (Nor), hepatic cancer induced control group (Con), and IJS extract 250 mg/kg administered group (IST) after being injected with DENA. Thereafter the changes of body weight, liver weight and weight of liver/100g body weight, the activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and superoxide dismutase (SOD) were measured. Gross anatomy and optical microscopy were also observed. Results : The body weight decreased in Con and IST compared with the Nor. The weight of liver and the weight of liver/100g body weight increased significantly in Con and IST compared with the Nor. The activities of AST, ALT, ALP, LDH increased in the Con compared with Nor, but decreased in IST compared with Con. The activities of SOD increased in the Con and IST compared with Nor. Upon naked eye and light microscopic examination, IJS improved the morphological and histopathological changes of liver caused by DENA-induced hepatic neoplasm. The number of hepatic p53 positive cells decreased in the IST compared with Con. Conclusions : Most of the results did not show a significant effect, but some of the results showed a significant effect. It can be estimated that IJS has some effects on hepatocellular carcinogenesis induced by DENA in rats, and further studies will be needed.