The assessment of therapists' behaviour an essential part of psychotherapy research, especially for controlling the validity of studies. In the last decade, particularly in English-speaking countries, research has been developed that studied two constructs important in this context: adherence and competence. Adherence refers to the extent to which therapists use the strategies recommended in a therapy manual; competence refers to the quality of the use of these strategies. This article is a review of research associated with adherence and competence scales and its relevance. First of all, definitions and examples of use are presented and discussed. Secondly, some of the most important scales that have been developed in this context are described. Thirdly, aspects of realisation are presented. Finally, the pros and cons of this type of research are discussed. It is argued that despite some problems adherence and competence scales are a significant contribution to the systematic assessment of therapist behaviour.