Immunoglobulin therapy is becoming an important modality for the prevention and treatment of bacterial and viral infection. Standard intravenous immunoglobulin (IVIG) is made from large pools of plasma obtained from normal blood donors. However, lot-to-lot variation in titers of antibody to specific microbial pathogens may diminish therapeutic efficacy. Since group B Streptococcus (GBS) is an important neonatal pathogen, a preparation with high titers of activity against GBS was prepared and studied. Plasma was obtained from volunteers immunized with a polyvalent GBS vaccine and was processed by the Swiss Red Cross for intravenous infusion. This high-titered GBS intravenous immunoglobulin (GBS-IVIG) was shown to be superior both in vitro and in vivo to standard IVIG. GBS-IVIG provided protection when therapy was delayed for up to 24 hours after infection. Standard IVIG did not protect animals against all GBS strains. However, GBS-IVIG enhanced survival from infection with all strains tested, even when the challenge dose of GBS was increased by 2 log units. Specific hyperimmune globulins to pathogens such as Haemophilus influenzae and Streptococcus pneumoniae have also been studied. Immunization of adult volunteers as a means of obtaining hyperimmune globulin appears to be an effective method of producing high-titered pathogen-specific preparations of IVIG.