This study is prospective study of newly diagnosed LTBI in HCWs at Hanyang University Hospital, a tertiary referral hospital in South Korea, between 2017 and 2018. This study aimed to identify the prevalence of adverse reactions of treatment regimen for LTBI. The diagnosis of LTBI was made on the basis of interferon-gamma releasing assay. Information on demographic characteristics, comorbidity and treatment outcomes was collated from questionnaires. Treatment regimen for LTBI was chosen by patients' preference among 3 months of INH(isoniazid) plus RFP(rifampin), 4 months of RFP and 9 months of INH. All PTB patients were observed 2 weeks after the initiation of medication, and monthly thereafter, and were asked about any drug side effects at these visits. Serious adverse drug reaction (ADR) was defined as any severe side effect that resulted in discontinuation or change (either temporally or permanently) of anti-TB medication, and/or directly resulted in hospitalization. Drug-induced hepatitis was defined as liver transaminases more than three times higher than the upper limit of normal in the presence of symptoms such as anorexia, nausea, vomiting, or abdominal pain, or transaminases more than five times the upper limit of normal without symptoms.