A 35-year-old Caucasian woman with proven systemic lupus erythematosus (SLE) had been effectively managed with hydroxychloroquine and methylprednisolone for many years. In 2005 she was admitted to the rheumatology clinic with a flare up of the disease and with proteinuria of 3.2 g/24 h. Renal biopsy was performed and revealed diffuse proliferative nephritis. Before the renal biopsy a positive HBsAg was found with high virus replication (hepatitis B virus (HBV)-DNA—4 170 000 copies/ml). Liver biopsy revealed chronic hepatitis with minimal activity (TAIS=1). Lamivudine was administered with concomitant maintenance corticosteroid treatment, but without antimalarials. Pulsed methylprednisolone treatment for diffuse lupus nephritis was begun on the background of lamivudine therapy. The liver enzymes returned to normal values, HBV replication was suppressed, and the proteinuria disappeared. At present the patient is not being treated with lamivudine and there are no objective signs of nephritis and hepatitis, or HBV activation.