In studies of the keeping quality of pasteurized milk, it was found that past records from milk plants showing good bacterial counts of finished products, afforded a rather reliable indication that milk from such plants may show better keeping quality than milk from plants with poor past records. Proper pasteurization resulted in extensive if not complete destruction of psychrophiles. Negative coliform counts of freshly pasteurized milk were not reliable as indicators of good keeping quality during storage at the temperature used in these studies. The mere absence of psychrophiles in one or two milliliters of milk was not found to be a guarantee of long storage life. The presence of aureomycin in the concentration used in these studies had no effect in extending the keeping quality of pasteurized milk.