Background: Little information exists on relapse in patients with bulimia nervosa who responded with complete abstinence from binge eating and purging to cognitive behavioral therapy. Identification of relapse predictors may be useful to design effective early intervention strategies for relapse of susceptible patients with bulimia nervosa. Methods: This multisite study examined relapse in 48 patients with bulimia nervosa who had responded to cognitive behavioral therapy with complete abstinence from binge eating and purging. Structured interviews and questionnaires were used to assess patients before and after treatment and at 4 months after treatment. Results: Four months after treatment, 44% of the patients had relapsed. Those who relapsed had a higher level of preoccupation and ritualization of eating and less motivation for change, and had maintained abstinence for a shorter time during the treatment period. Conclusions: The predictors of relapse found in this study can be readily determined by clinicians. The effectiveness of early additional treatment interventions needs to be determined with well-designed studies of large samples.