Objective: To describe the relative effectiveness of a short versus long course of family-based therapy (FBT) for adolescent anorexia nervosa at long-term follow-up. Method: This study used clinical and structured interviews to assess psychological and psychosocial outcomes of adolescents (ages 12-18 years at baseline) who were previously treated in a randomized clinical trial using family therapy between 1999 and 2002. Results: Eighty-three percent (71/86) of subjects participated in follow-up assessments of current psychological and psychosocial functioning. In addition, 49% (35) were interviewed using the Eating Disorder Examination. Mean length of follow-up was 3.96 years (range 2.3-6.0 years). There were no statistically significant differences between the two groups on any measure at long-term follow-up. As a whole, the group was doing well with 89% above 90% ideal body weight, 74% with Eating Disorder Examination scores within the normal range, and 91% of postmenarcheal females not on birth control had menstrual return. Conclusions: A short course of family therapy is as effective as a longer course at follow-up. (Contains 5 tables.)