We investigated the relation between diet pill use and eating disorder subtype, purging and other compensatory behaviors, body mass index (BMI), tobacco and caffeine use, alcohol abuse or dependence, personality characteristics, and Axis I and Axis II disorders in 1,345 participants from the multisite Price Foundation Genetics Studies. Diet pill use was significantly less common in women with restricting type of AN than in women with other eating disorder subtypes. In addition, diet pill use was associated with the use of multiple weight control behaviors, higher BMI, higher novelty seeking, and the presence of anxiety disorders, alcohol abuse or dependence, and borderline personality disorder. Findings suggest that certain clinical and personality variables distinguish individuals with eating disorders who use diet pills from those who do not. In the eating disorder population, vigilant screening for diet pill use should be routine clinical practice.