A mouse model was developed to test the efficacy of human immune globulin intravenous (IGIV) in prevention and treatment of pneumococcal bacteremia. Mice pretreated with IGIV and then challenged with types 3 or 7F Streptococcus pneumoniae had significantly increased (P less than 0.025) survival compared to controls. Three commercially available IGIV preparations were all effective in significantly increasing (P less than 0.025) survival in mice already infected. Mice treated with IGIV plus penicillin had significantly greater (P less than 0.05) survival than those who received penicillin alone. IGIV may be useful in treatment of pneumococcal bacteremia.