The aim of this study was to test the effectiveness of a cognitive-behavioral guided self-help treatment program for bulimia nervosa and similar disorders. Participants were assessed at the beginning and end of treatment, and at 6 months follow-up, using the Eating Disorder Examination Questionnaire (EDE-Q), the Outcome-Questionnaire-45 (OQ-45), and the Beck Depression Inventory (BDI). Forty-two participants from an eating disorders treatment service participated in this study. This study followed a one-group repeated measures naturalistic design with no control group. Results showed a significant reduction in EDE scores, OQ-45 and BDI. Clinically significant change occurred for the majority of participants. Cognitive-behavioral self-help treatment may be of value as an initial treatment for bulimia nervosa and similar disorders such as binge eating disorder.