Milk samples of five breast-feeding mothers were studied for bacterial population, flora, and source. In most instances, samples taken at postfeeding contained higher bacterial populations than prefeeding samples. Staphylococcus epidermidis was the predominant organism isolated from 100% of the samples. Increases were noticed in the appearance of Streptococcus mitis , Gaffkya tetragena , Streptococcus salivarius , Staphylococcus aureus , as well as Lactobacillus acidophilus , in the postfeeding samples. Main sources of bacteria were found to be the infant's mouth and maternal skin.