Current screening instruments for eating disorders are cumbersome to administer and have not been validated in primary care populations. We compared the performance characteristics of 2 screening tools, the SCOFF clinical prediction guide, and a new set of questions, the Eating disorder Screen for Primary care (ESP), using the Questionnaire for Eating Disorders Diagnosis as the independent standard, in 104 consecutive patients from a primary care practice and 129 university students. Twelve percent of the combined population had an eating disorder. One or no abnormal responses to the ESP ruled out an eating disorder (likelihood ratio [LR] 0.0), whereas 3 or more abnormal responses ruled one in (LR 11). The SCOFF questions were less sensitive than predicted (1 or no abnormal responses, LR 0.25), but were as effective at ruling in an eating disorder (3 or more abnormal responses, LR 11).