Steam-distillation of dry whole milk was found to be an effective means of separating the products of fat oxidation preparatory to reacting them with 2-thiobarbituric acid (TBA). The milk powder samples were reconstituted and acidified prior to steam distillation. A fraction of the distillate was reacted with the reagent to produce the red-colored product, which was then estimated spectrophotometrically at 530 mμ. Factors which influence the sensitivity and reliability of the method were investigated. The method is rapid and reproducible, and the test solutions are free of turbidity. The reaction is a measure of the oxidation of dry whole milk, and when it was applied to samples from storage, the results had validity in terms of flavor.