Background: The purpose of this study was to evaluate the effects of a nutrition education program designed to teach elementary school students and their parents, and to distinguish between more healthful and less healthful choices in diverse food categories. Methods: Three schools were assigned to receive the Nutrition Detectives[TM] program and 2 comparable schools served as controls. A total of 1180 second, third, and fourth grade elementary school students were included, with 628 students in the intervention and 552 in the control group. The program, delivered by physical education instructors over several sessions totaling less than 2 hours, taught the children how to read food labels and detect marketing deceptions, while learning to identify and choose healthful foods. Parents were introduced to the program through written materials sent home and at school functions. Assessments included a food label quiz, dietary pattern, and body mass index (BMI). Results: Students in intervention schools showed a significant increase in nutrition label literacy (p less than 0.01). Third grade students showed the most improvement, 23% (p less than 0.01). The parents of intervention group students also showed a significant increase in nutrition label literacy by 8% (p less than 0.01). Total caloric, sodium, and total sugar intake decreased nonsignificantly among students in the intervention group (p greater than 0.05). BMI did not change over the short duration of the study. Conclusions: Nutrition Detectives effectively enhances the ability of students and their parents to identify more nutritious food choices. Further evaluation of the program and its potential to influence dietary pattern, BMI, and health outcomes in students and their families is warranted. (Contains 3 tables and 1 figure.)