The external validity of behavioral treatments for elopement (i.e. leaving supervision without permission) remains unclear because studies to date include only small samples (n = 1–3). This study quantified the overall effectiveness of behavioral treatments for elopement by retrospectively examining treatment data from all patients seen for the treatment of elopement at an intensive day treatment clinic (n = 11), irrespective of treatment success. Reductions in elopement from baseline to the final treatment for each participant demonstrate that behavioral intervention is a highly effective treatment for elopement, as determined by the large effect size (Cohen’s d = 1.18).