In a prospective controlled study the anti-infective properties of breast-milk were evaluated in 70 high-risk low-birth-weight infants. 32 babies (group I) were given fresh expressed breast-milk during the day and milk formula at night. 38 infants (group II) received only milk formula and served as controls. The two groups were matched for other factors that could influence the occurrence of infection. The incidence of infections was significantly less (p < 0.01) in babies who received breast-milk.