The authors conducted 4 studies investigating the reliability and validity of the Eating Disorder Diagnostic Scale (HDDS; E. Stice, C. F. Telch, & S. L. Rizvi, 2000), a brief self-report measure for diagnosing anorexia nervosa, bulimia nervosa, and binge eating disorder. Study 1 found that the HDDS showed criterion validity with interview-based diagnoses, convergent validity with risk factors for eating pathology, and internal consistency. Studies 2 and 3 found that the EDDS was sufficiently sensitive to detect the effects of eating disorder prevention programs. Regarding predictive validity, Studies 3 and 4 found that the EDDS predicted response to a prevention program and future onset of eating pathology and depression. Results provide additional evidence of the reliability and validity of this scale and suggest it may be useful in clinical and research applications.