The apparent increase in frequency of neonatal necrotizing enterocolitis1 and the recognition that the gastrointestinal tract is often the portal of entry in neonatal sepsis2 has renewed interest in breast milk as a source of newborn immunity. Attention has recently focussed on milk leukocytes. The purpose of this commentary is to summarize the available information on this subject and to examine the implications that this knowledge may have on the possible use of human milk-feeding to protect the newborn from infection. Human colostrum and early milk contain 1 to 2 x 106 leukocytes; 80% to 90% of these are monocytic phagocytes and the remainder are lymphocytes.3,4