To estimate the efficacy of intravenous gamma globulin adjunct therapy on the course of severe neonatal group B streptococcal (GBS) disease, the hospital records of 67 confirmed cases of early-onset GBS sepsis associated with neutropenia were reviewed. Among the 33 infants who had received antibiotic agents without gamma globulin, 13 (39%) died. Among the 34 who had received antibiotic agents plus gamma globulin, 6 (18%) died (p < 0.05). Among 52 low birth weight infants, 5 (20%) of the 25 given gamma globulin died compared with 13 (48%) of the 27 not given gamma globulin (p < 0.03). Neutrophil counts rose more rapidly among survivors who received gamma globulin than among those who did not. This retrospective study suggests that intravenous gamma globulin adjunct therapy for neonatal GBS disease associated with neutropenia promotes a more rapid increase in neutrophil count and improves survival.