This article applies and illustrates the American Group Psychotherapy Association (AGPA) revised CORE battery to daily practice. The CORE can assist practitioners in periodically or continuously monitoring outcome and process factors to determine patient status (e.g., improved, deteriorated, or no change), and ruptures in the therapeutic relationships. The CORE-R provides group therapists with a tool kit of measures for assessing the effectiveness of their groups and includes three classes of measures: selection, process, and outcome. We provide a summary of each class of measures along with specific instruments. © 2008 Wiley Periodicals, Inc. J Clin Psychol: In Session 64:1–13, 2008.