In a study of 36 patients with anorexia nervosa (age at onset: 14.5 +/- 1.9 years), an attempt was made to predict longterm outcome (follow-up interval: 7.8 +/- 3.77 years) from weight changes during inpatient treatment (duration of treatment: 156 +/- 76 days). Several statistical methods appropriate for use with longitudinal data were applied. The long-term course could be predicted correctly for 96% of the patients with a good or intermediate outcome (prognostic criteria of Morgan and Russel) and for 89% of those with a poor outcome. The most important factors predictive of a good outcome were relatively long time to stabilization of weight (greater than 47 days), a stabilized weight of at least 64% of ideal weight, low age at onset (less than 13 years) and a high variability in weight during inpatient treatment as compared with patients who had a poor prognosis.