• Unprocessed breast milk is currently being used as a desirable feeding alternative for premature infants. To assess some of the potential risks of this practice, we studied the bacterial growth in 41 samples of unprocessed human milk for a period of five days. No bacteria Were cultured in eight samples of milk; the bacteria that were cultured in the remaining 33 samples were similar to those found on the skin and nipple of the breast. With the exception of three samples, two with Klebsiella and one with Pseudomonas, all identified bacteria have been reported as normal skin flora. The initial concentration of bacteria found in milk was low, with a mean of 10 000 colonies (range, 1000 to 140000 colonies). Bacterial colony counts progressively decreased throughout the five-day refrigeration period.