Objective To determine the effect of dimethyl-4, 4'-dimethoxy-5, 6, 5', 6-dimethylene dioxybiphenyl-2, 2'-dicarboxylate (HpPro) on patients with acute and chronic liver diseases.Methods An open trial and a prospective randomized and controlled study were performed. The open trial consisted of 56 cases (16 cases of acute hepatitis, 20 cases of chronic hepatitis, 14 cases of liver cirrhosis and 6 cases of fatty liver). Controlled study consisted of 20 cases of Child A chronic hepatitis which were randomly treated with either HpPro or a mixture of known drugs which used as a liver protective agent in Indonesia as control for one week. The patients were then crossed over those two drugs in the next week. Results In the open trial, after 4 weeks' treatment with HpPro 7.5 mg orally three times daily, acute hepatitis, chronic hepatitis and fatty liver cases showed rapid decrease of SGOT and SGPT. In the liver cirrhosis cases, SGOT and SGPT were decreased slowly. In the controlled trial, nine patients received HpPro 7.5 mg three times daily orally and eleven were treated with a mixture of known drugs as the controls. After one week treatment, HpPro group clinically showed significant decrease of SGPT and SGOT levels compared to control group (P=0.035). At the second week, HpPro group showed significant decrease of SGOT compared to control group (P=0.038) but the decrease of SGPT was not significant (P=0.096). Conclusion Treatment with HpPro is effective to reduce liver impairment in acute and chronic liver diseases on Indonesian patients. No side effect of HpPro was observed.