BACKGROUND: Abnormal liver function was found in pa- tients with severe acute respiratory syndrome ( SARS). This study was undertaken to explore the clinical characteris- tics and mechanisms of liver damage. METHODS: The serial laboratory data of liver function test and hepatic histological examination from 168 patients with SARS were retrospectively analyzed. RESULTS: The abnormalities of serum alanine aminotrans- ferase (ALT) were 52.5%, 71.8%, 85.7% and 85.2%. The average levels of ALT of the patients were 56.07 ±51.57 U/ L, 86.46±69.93 U/L, 106.69± 102.50 U/L and 111.32± 160.24 U/L, and the average levels of serum albumin were 37.25±5.37 g/L, 35.82±4.74 g/L, 34.49±5.04 g/L, and 34.26±4.70 g/L, at the day of admission, the first week, second week, and third week after hospitalization, respec- tively. Significant correlation was not shown among liver damage, blood oxygen saturation (SaO2), degree of fever, and immune functional disorder in this study. Hepatic his- tological examination of 4 patients demonstrated that non- specific inflammation existed in the liver. CONCLUSIONS: Liver damage of patients with SARS usu- ally occurs in the early stage of the disease with a high oc- currence rate and a prolonged profile, which can be charac- terized by early, obvious decrease of albumin levels and slightly abnormal levels of ALT. The liver damage induced by SARS seems to be caused by SARS virus directly rather than by low SaO2 or high fever. Hepatotoxic drugs may play a role in increasing the severity of liver damage or pro- longing the time of liver function recovery. BACKGROUND: Abnormal liver function was found in pa- tients with severe acute respiratory syndrome (SARS). This study was undertaken to explore the clinical characterisics and mechanisms of liver damage. METHODS: The serial laboratory data of liver function test and hepatic histological RESULTS: The abnormalities of serum alanine aminotransferase (ALT) were 52.5%, 71.8%, 85.7% and 85.2%. The average levels of ALT of the patients were 56.07 ± 51.57 U / L, 86.46 ± 69.93 U / L, 106.69 ± 102.50 U / L and 111.32 ± 160.24 U / L, and the average levels of serum albumin were 37.25 ± 5.37 g / L, 35.82 ± 4.74 g / L, 34.49 ± 5.04 g / L, and 34.26 ± 4.70 g / L, at the day of admission, the first week, second week, and third week after hospitalization, respec tively. Significant correlation was not shown among liver damage, blood oxygen saturation (SaO2), degree of fever, and immune functional disorder in this study. Hepatic his- tological e xamination of 4 patients demonstrated that non- specific inflammation existed in the liver. CONCLUSIONS: Liver damage of patients with SARS usu- ally occurs in the early stage of the disease with a high oc- currence rate and a prolonged profile, which can be charac - terized by early, obvious decrease of albumin levels and slightly abnormal levels of ALT. The liver damage induced by SARS seems to be caused by SARS virus directly rather than by low SaO2 or high fever. Hepatotoxic drugs may play a role in increasing the severity of liver damage or pro- longing the time of liver function recovery.