Treatment fidelity refers to the extent to which treatments are delivered according to the treatment protocol or manual. Though commonly used in research, it is argued that fidelity is also relevant in routine practice in terms of how evidence based therapies are delivered. For this, fidelity measures are required that are suitable for monitoring treatment delivery in front line services. Methods of evaluating practice in the addictions field have typically been designed to measure fidelity to specific treatments in research trials and are therefore not well suited to monitoring in routine practice, where therapists may use more than one therapeutic approach and be restricted in terms of time and resources. I will discuss the development of the Addiction Therapist Rating Scale (ATRS), a tool designed to evaluate delivery of psychological therapies used in routine practice for alcohol and drug use problems. The ATRS project is funded by the Society for the Study of Addiction and Alcohol Research UK.