Attenuated total reflectance (ATR), offering a possible rapid method for quantitative measurements of major nutritional components in food materials (fat, protein, carbohydrate), was employed to evaluate the composition of a variety of soy products. Using a sample cell developed in this laboratory, different sample particle sizes and forces applied to a mounted sample were investigated to determine if variations of this type would improve the accuracy and precision of the quantitative ATR technique. Correlations of 0.96 for fat and 0.94 for protein were achieved between a chemical analysis and the infrared technique using a baseline absorbance (A′) calculation and 120 mesh samples at 40 lb force. Errors assignable to various aspects of the ATR technique are discusse