Few if any reliable indicators of long-term outcome have been found in eating disorders. Impulsivity was the strongest predictor in the present study of 35 adults with anorexia nervosa or bulimia nervosa. This variable accounted for 25% of anorectic symptoms at 2 to 3 years follow-up and 14% at 4 to 6 years (Eating Attitudes Test). The relationship was specific insofar as impulsivity predicted neither depression nor overall mental health. Cognitive impairment may be one reason for the poor prognosis of impulsive patients.