Sepsis and pneumonia continue to be major causes of morbidity and mortality in newborn intensive care, units. This largely reflects increasing survival rates for extremely immature, low-birth-weight neonates (<1 kg). These babies manifest gross defects in cellular and humoral immunity and are extremely susceptible to infection. Because so much attention has been focused on the use of intravenous immunoglobulin to reduce the incidence of infection in these infants, I summarize the concept of the low-birth-weight infant as a compromised host and provide an update on the use of intravenous immunoglobulin in these babies.