The value of IgM-enriched immunoglobulin therapy in 44 preterm infants with neonatal sepsis was evaluated in a prospective randomized study. All infants received antibiotic therapy and fresh plasma and/or whole blood transfusions. Twenty randomly-chosen infants were allocated to receive 5 ml/kg/d of IgM-enriched immunoglobulin intravenously for three days. Although the mortality rate in preterm infants whose gestational ages were 31-34 weeks in the immunotherapy group was slightly lower than in the control group, the general mortality rate from sepsis in the control group (9/24) and in the immunotherapy group (6/20) showed no statistically significant difference (37.5% vs 30.0%, p < 0.05).