In brief: A total of 348 coaches, 179 athletic trainers, and 2,977 athletes in high school and college settings answered questionnaires about their nutrition knowledge and practices. Certified athletic trainers had the best nutrition backgrounds, and they believed they should take primary responsibility for athletes' nutrition. Coaches and athletic trainers are most concerned about fluid intake, but athletes are most concerned about weight. Most athletes are familiar with and use the basic four food groups, but 44% take vitamin supplements, 13% take mineral supplements, and 9% take protein supplements.