Hepatitis B is endemic in many Asian countries and immunosuppression may precipitate hepatitic flare. There is little data on the treatment of hepatitis B in patients with systemic lupus erythematosus. We monitored serial transaminase and HBV DNA levels in our HBsAg-positive patients with a history of lupus nephritis and instituted anti-viral treatment in patients who showed virological reactivation. This retrospective pilot study reports the data with this pre-emptive management strategy. Amongst 228 patients with lupus nephritis, eight (3.51%) were HBsAg-positive and five had received Lamivudine treatment for hepatitis B. In two patients the virological flares were preceded by lupus flares that necessitated an increase in immunosuppressive treatment. Median HBV DNA level was 1.9 x 10(7) copies/mL (range 1.2 x 10(4)-1.0 x 10(9) copies/mL) at baseline, and it decreased by 2-5 logs after treatment. Four patients had abnormal transaminase levels at baseline, with mean alanine aminotransferase at 125.0 +/- 67.4 U/L, and all achieved normalisation after 3-24 months (median 13 months) of treatment. Discontinuation of Lamivudine treatment was attempted in three patients after 9-15 months. In one patient treatment was recommenced because of virological flare. For the remaining two patients in whom treatment was not interrupted, one showed sustained viral suppression and one developed drug resistance. All antiviral treatments were well-tolerated. These results indicate the importance of serial monitoring of HBV DNA and transaminase levels, and prompt anti-viral therapy, in the management of HBsAg-positive lupus patients. Also, it may be feasible to discontinue treatment in stable patients to avoid the selection of drug-resistant variants.