Herbal hepatotoxicity is a one of the most often encountered controversial issues in medical society. Some believe herbs are totally safe while others regard treatment with herbs as a very common cause of hepatotoxicity. But there are no comparative clinical hepatotoxicity studies between herbal and conventional medicines. We investigated incidence of patients with abnormal liver function who were treated with herbal or conventional medicine at Dongguk University International Hospital. Each group consisted of 300 patients, who were admitted for longer than 30 days during the year 2008. We compared albumin, total bilirubin, AST (aspartate aminotransferase), and ALT (alanine aminotransferase) levels, and excludes patients who had abnormal liver function test or liver-related disease when admitted. As a result, incidence of total bilirubin, AST, and ALT elevation in the CT (conventional treatment) group was more frequent than in the TKM (traditional Korean medicine) group (p<0.05) during admission. Albumin level also decreased more frequently in the CT group than in the TKM group (p<0.05). According to these results, herbal medicine is not more hepatotoxic than conventional medicine, and not a main cause of liver injury in inpatients.