Summary A new method has been devised for determining the solubility of milk powders. It is sensitive to differences in solubility of powders which are too soluble to be differentiated by the method of the American Dry Milk Institute. The new method differs from the ADMI method in the following features:1. All of the reconstituted sample is used in the test instead of only a portion. 2. Reconstitution is by a standardized shaking procedure which puts into suspensionless of the difficultly soluble material than does the vigorous mechanical stirring in the ADMI method. 3. The undissolved material separated by centrifugation of the reconstituted sample is dried and the amount is determined gravimetrically. 4. The results can be calculated to give the solubility index in terms of per cent of soluble material. The method gives results that can be reproduced within a narrow range on repeated trials by the same operator or by different operators.