Of unselected postpartum women, 39% reactivated cytomegalovirus in breast milk, vaginal secretions, urine, and/or saliva. Consumption of infected breast milk led to infection of 69% of the infants. Although there was some milk secretory immune response to this virus, it prevented neither viral shedding nor viral transmission. All infected infants chronically shed cytomegalovirus. However, no infants have yet demonstrated chronic sequelae. Two preterm infants did develop a significantly acute problem, pneumonitis, which did resolve. The possibility that an unnecessary and perhaps more severe illness might occur in low-birth-weight seronegative infants fed banked human milk from sources other than the mother is disturbing and needs resolution.