In a pilot study, core beliefs and underlying assumptions were investigated in patients with bulimia nervosa, patients with depression and female controls, using a new self-report measure. The patients with bulimia nervosa did not differ from the patients with depression in negative self beliefs but they did differ in assumptions concerned with weight, shape and eating. Both groups of patients also differed from the female controls, with the exception of one comparison including the depressed patients. The findings support recent developments in cognitive theories of eating disorders. Treatment implications are briefly discussed.