Using a retrospective chart review of patients with anorexia nervosa, we matched 23 inpatients and 23 patients in intensive outpatient treatment by diagnosis and age, comparing admission and discharge weights, lengths of stay, and rates of weight gain. The inpatient and outpatient groups did not differ significantly on age, age at onset of eating disorder, or duration of illness. The inpatient group weighed significantly less at admission than the outpatient group (mean percent of ideal body weight=71%, SD=9, versus mean=80%, SD=6) (t=–4.0, df=44, p<0.0001). However, the inpatients gained 15% of their ideal body weight during 46 days (SD=27) of hospitalization, at a rate of 0.3% of ideal body weight per day. By comparison, the patients in intensive outpatient treatment gained only 1.4% of ideal body weight during 69 days (SD=45) of treatment, at a rate of 0.01% of ideal body weight per day (difference in weight gain: t=5.9, df=44, p<0.0001).