Increasing interest in feeding human milk to low-birth-weight infants raises concern about microbial contamination of milk that is pooled or stored. We examined the effect of rapid high-temperature treatment on bacteria and viruses and on the nutritional and immunologic quality of pooled human milk. Growth of endogenous bacteria and infectivity of added cytomegalovirus were undetectable after heating at 72 degrees C for 15 and 5 seconds, respectively. Folic acid and vitamins B1, B2, B6, and C were not affected, whereas bile salt-stimulated lipase was inactivated by these conditions. The concentration of lactoferrin and secretory IgA, and SIgA antibody activity were not changed by heating at 72 degrees C. Lysozyme concentration and enzymatic activity were increased significantly by heat treatment, suggesting that this component may be largely sequestered in milk. Our findings suggest that rapid high-temperature treatment can reduce microbial contamination without destroying the unique nutritional and immunologic qualities of human milk.