In order to register data on costs for episodes of acute hepatitis B virus (HBV) infection in adults, the medical records from 70 adults with acute HBV infection seen at Roslagstull's Hospital in Stockholm, Sweden, were reviewed. All cost-consuming events due to medical treatment, absence from work, and secondary prophylaxis were registered. The average cost was 1,230 pounds for medical treatment, 570 pounds for work loss and 290 pounds for secondary cases and prophylaxis, a total of 2,090 pounds in 1992 prices. This figure is considerably lower than that reported in 3 previous European studies. Accurate estimates of the costs for a case of HBV, as well as those of different vaccination strategies, are essential when economic aspects of HBV vaccination programmes are discussed.