Objective To investigate the prevalence of HBV infection and the risk of hepatitis B virus (HBV) reactivation in patients with inflammatory arthritis receiving tumour hecrosis factor alpha (TNFα) inhibitors.Methods The liver function,serology of HBV and viral loads (HBV DNA) were tested before using TNFα inhibitors,at 3 months and 6 months.Patients with chronic hepatitis B (CHB) infection (HBV DNA ＞ 1 × 103copies/ml) were eliminated.Results A total of 162 patients were investigated including 156 patients who finished the study.Eleven (7.05％) patients were HBsAg-positive.Two patients with HBV DNA ＞ 1 × 103copies/ml were eliminated before starting anti-TNFα therapy.Among HBsAgpositive patients,HBV reactivation was documented in only one of the 11 patients.This patient with rheumatoid arthritis developed elevation of glutamic-pyruvic transaminase (ALT) and HBV DNA copies three months after infliximab therapy.Therefore lamivudine was given for three months,which translated into the fall of ALT and HBV DNA copies back to normal level.After follow-up for six months,the virology and serology remained stable.In contrast,none of the other 155 patients had demonstrated evidence of HBV infection or HBV reactivation.Conclusion The kinetics of HBV viral loads should be carefully monitored in patients with inflammatory arthritis and HBsAg-positive during anti-TNFα therapy.HBV reactivation should be treated with antiviral medicine through out the period of anti-TNFα therapy.