This report describes research that Mathematica Policy Research, Inc. (MPR) has conducted for the U.S. Department of Agriculture (USDA), Food and Nutrition Service (FNS), to develop methods to track the use of "competitive foods" in schools over time. Competitive foods are foods from a la carte cafeteria sales, vending machines, school stores, snack bars, and similar sources that do not qualify as reimbursable meals under the National School Lunch Program (NSLP) or the School Breakfast Program (SBP). FNS is interested in obtaining more precise information than is currently available about the nature, extent, and implications of the use of competitive foods. In response to this need, this study has identified the issues and problems associated with the collection, analysis, and interpretation of data on competitive foods. It has also examined the availability and nutritional quality of competitive foods. Insights drawn from the study will provide a foundation for planning future school nutrition monitoring activities designed to ensure that the nation's school children have access to healthful food choices throughout the school environment. Appended are: (1) Data Collection Instruments; (2) Details of Sampling Methods; (3) Selection of Food and Beverage items Offered in Vending Machines; and (4) A La Carte Food and Beverage Items Offered in Cafeteria Lines. [Report submitted to the Office of Analysis, Nutrition and Evaluation.]