Liver toxicity is a common side effect of antituberculosis (anti-TB) drugs. We studied the differences in liver dysfunction observed during anti-TB treatment between hepatitis B virus carriers (HBV) and noncarriers. Three hundred twenty-four patients on anti-TB drugs were recruited and followed up for 1 year. Forty-three patients with HBV and 276 non-HBV patients were included for analysis. Liver function tests and viral markers were monitored monthly. Liver biopsy was requested whenever the alanine transaminase (ALT) was persistently abnormal. Eighty-six HBV carriers who were not given anti-TB drugs were chosen as a second control and evaluated prospectively. The incidence of liver dysfunction was significantly higher in HBV carriers given anti-TB drugs (34.9%) when compared to noncarriers (9.4%, P < .001) and with HBV carriers not given anti-TB drugs (8.1%, P < .001). For patients given anti-TB drugs, HBV carriers who developed liver dysfunction were younger (P = .011) and had more severe liver injury compared with noncarriers (P = .008). By multiple logistic regression analysis, age (P = .002) and hepatitis B infection (P < .001) were the only 2 significant risk factors for hepatotoxicity related to anti-TB therapy.