This report describes the proposed intervention and outcome measurement procedures for the Pathways study. Pathways is a multicenter school-based study aimed at reducing the alanning increase in the prevalence of obesity in American Indian children. It is designed as a randomized clinical trial, involving approximately 2,00 third grade children in 40 schools in seven diferent American Indian communities. During a 3-year feasibility phase, which was just completed, the major components of the intervention (school food service, classroom curriculum, physical education program, and family involvement) were developed and pilot-tested. The measurement instruments for body composition; physical activity; dietary intake; and knowledge, attitudes, and behavior were also developed and validated. Comprehensive process evaluation procedures also were defined. As of this writing, thefull-scale intervention program is being initiated and is scheduled to be completed in the spring of 200. The primary aim of the Pathways intervention is to reduce average percent body fat in intervention-school children by at least 3% compared with control-school children by the end of the 3-year intervention. This goal is to be achieved primarily by an increase in physical activity and a reduction in the perceni of dietary fat intake. The program does not seek to reduce dietary energy intake. Rather, it is based on the assumption that a healthier; lower-fat diet, combined with an increase in energy expenditure by increased physical activity, will result in fewer excess calories deposited as body fat.