Background. This paper describes the methods used in 'High 5,' a school-based study to increase fruit and vegetable consumption for cancer risk reduction. Methods. Twenty-eight elementary schools were matched and randomized to intervention or control conditions. All students were assessed based on diet and psychosocial variables at baseline and one and two years post-baseline. The intervention included classroom, parent, and environmental components. Results. The study recruited 1,698 families and retained 85%. The two conditions were equivalent at baseline; 50% female students, 81% to 84% European-American students, and 2.9 servings of fruit and vegetables per day. Good completion was achieved across the intervention components (e.g., 90% of lessons taught, 72% of parent materials read, 3.6 servings of fruit and vegetables offered in cafeterias). Conclusions. The use of school-based programs, with strong evaluation designs, will enhance knowledge about the modification of nutrition behavior and cancer risk in children. Lessons learned from the study are reported.