The number of people diagnosed with substance abuse and dependence continues to increase with serious implications for individuals and groups.Addiction treatment can be effective, and certain principles, when adhered to, increase the likelihood of success: engagement, retention and individualization.Becker's Health Belief Model (HBM, 1974) has been used successfully to address behavior change in chronic diseases, as well as smoking and alcohol dependence. This project applies the HBM to opiate addiction treatment, specifically medication assisted treatment (MAT). The purpose of this study was to measure the relationship between self-efficacy and treatment outcomes for opiate dependent clients on MAT. A convenience sample of 50 persons with addiction to opiates was admitted to an outpatient substance abuse treatment program for MAT using methadone, and followed for a period of 6 months. Preand post-treatment self-efficacy scores were obtained using a modified General Self-Efficacy Scale (GSE; . Treatment outcomes were measured by the number of negative random monthly urine screens, attendance at group and individual counseling sessions, daily dosing adherence, and retention in treatment for at least 6 months. Pre-and post-treatment selfefficacy scores were compared using a t-test, and self-efficacy scores were compared to client outcomes using Pearson Correlation. GSE scores demonstrated improvement after 6 months in treatment (p=<.01). However, no statistically significant relationship was found between GSE scores and treatment outcomes.