Investigators at 30 centers evaluated an intravenous hepatitis B immune globulin preparation in the therapy of fulminant type B hepatitis. Patients with serum positive for hepatitis B surface antigen were treated at stage II to stage IV of hepatic encephalopathy. A central computer program randomized cases for treatment with hyperimmune globulin or albumin placebo. During the first 6 months, the dose of hepatitis B immune globulin was 1.32 g of immunoglobulin G protein; during the last 7 months, it was 5.28 g. Neither dose eliminated antigenemia. In the placebo group, death occurred in four of eight cases randomized at stage II, five of eight at stage III, and 10 of 12 at stage IV. In the group treated with hyperimmune globulin, death occurred in three of five patients randomized at stage II, seven of 12 at stage III, and six of eight at stage IV. The study, therefore, showed no benefit of treatment with exogenous antibody.