This research was designed to test the reliability of modified Association of Official Analytical Chemists methods for quantitation of thiamine, riboflavin, and ascorbic acid in milk; to ascertain the extent of destruction of those vitamins by modern heat processing; and to determine if it is truthful to report that heat processing does not reduce milk's nutritional properties insofar as those vitamins are concerned. Milk was processed continuously at four time-temperature treatments, including that used for modern commercial sterilization. Both raw and heated milks were analyzed immediately for content of heat labile vitamins; subsamples were packaged in amber plastic bottles, frozen, and subsequently analyzed for vitamin content after 14 days storage. Analyses were by modified Association of Official Analytical Chemists fluorometric techniques.