OBJECTIVE This study examined the influence of primary care physicians' knowledge of and attitudes to eating disorders on their treatment decisions. METHODS A sample of primary care physicians completed self-report measures on eating disorders and their attitudes towards such patients. They also indicated their diagnosis and treatment decisions in response to case vignettes. RESULTS Physicians had substantial gaps in knowledge of the eating disorders. Attitudes to anorexia nervosa clustered differently to those toward patients with bulimia nervosa. However, for both disorders, the factor that explained the most variance was illness duration and consequences. There was no association of knowledge and attitudes, and these variables did not predicted the likelihood of diagnosing an eating disorder. However, those with higher knowledge scores were more likely to ensure that a follow-up appointment took place, particularly when they held the attitude that people with anorexia nervosa had personal control over their problem. CONCLUSIONS There is a need for greater education of primary care physicians regarding the diagnosis and treatment of the eating disorders, and for that information to be more readily accessible when it is needed. Their clinical actions need to be guided by more objective sources of information and protocols.