Objectives: The aim of this study was to identify the causal relationship between use of levocetrizine or cetrizine, and liver injury, by comparing frequency and pattern of hepatotoxicity in levocetrizine or cetrizine prescribed patients. Methods: This is a retrospective observational study, using data retrieved from electronic medical record system. Among 1164 patients prescribed levocetrizine or cetrizine during study period (Jul, 2009 - Jun, 2010) at Seoul National University Hospital, 543 patients with more than 4- time liver function test (LFT) results were included in final analysis. Liver injury was defined as greater than 3 times elevated level of alanine aminotransferase or 2 times elevated level of alkaline phosphatase or total bilirubin, compared to upper limit of normal, in patient with normal liver function at baseline. The frequency and pattern of liver injury were assessed. Results: Incidence of liver injury in patients prescribed with levotcetrizine or cetrizine were 1.48% and 2.94%, respectively. With few exceptions, most injuries were shown to be hepatocellular type. Rapid recovery was observed after drug cessation and long term use tends to be associated with incidence of liver injury. In patient with digestive system disorder, rate of liver injury was significantly higher (p=0.011). Conclusion: The result of this study implies potential need of liver toxicity monitoring, especially in patients taking long term levecetrizine or cetrizine or in patient with digestive system disorder. However, prospective large scale observational study is needed to confirm liver injury associated with the use of levocetirizine or cetirizine.