The present study evaluates the current BMI cut-off for diagnosing anorexia nervosa. Physical state, eating disorder and general psychopathology were compared in two groups diagnosed with anorexia nervosa, using ‘strict’ or ‘lenient’ weight criteria (above or below the generally accepted BMI cut-off of 17.5 kg/m2). Individuals in the lenient group had a higher percentage body fat and a greater discrepancy between current and ideal body weight, but there were no differences between the two groups on other body image measures. The strict group had met criteria for strict anorexia nervosa for a greater proportion of the past 5 years, but there was no difference in the number of months with anorexia nervosa. On all other variables, the two groups were indistinguishable. These results challenge the cut-off of BMI 17.5 kg/m2 in the diagnosis of anorexia nervosa. Copyright © 2004 John Wiley & Sons, Ltd and Eating Disorders Association.