Context: There have been very few randomized controlled treatment studies of anorexia nervosa. Objective: To evaluate factors leading to nonacceptance and noncompletion of treatment for 2 specific therapies and their combination in the treatment of anorexia nervosa. Design: Randomized prospective study. Setting: Weill-Cornell Medical Center, White Plains, NY; University of Minnesota, Minneapolis; and Stanford University, Stanford, Calif. Patients: One hundred twenty-two patients meeting DSM-IV criteria for anorexia nervosa. Interventions: Treatment with cognitive-behavioral therapy, fluoxetine hydrochloride, or their combination for 1 year. Main Outcome Measures: Dropout rate and acceptance of treatment (defined as staying in treatment at least 5 weeks). Results: Of the 122 randomized cases, 21 (17%) were withdrawn; the overall dropout rate was 46% (56/122) in the remaining patients. Treatment acceptance occurred in 89 (73%) of the 122 randomized cases. Of the 41 assigned to medication alone, acceptance occurred in 23 (56%). In the other 2 groups, acceptance rate was differentiated by high and low obsessive preoccupation scores (rates of 91% and 60%, respectively). The only predictor of treatment completion was high self-esteem, which was associated with a 51% rate of treatment acceptance. Conclusion: Acceptance of treatment and relatively high dropout rates pose a major problem for research in the treatment of anorexia nervosa. Differing characteristics predict dropout rates and acceptance, which need to be carefully studied before comparative treatment trials are conducted.