A unique characteristic of chronic diseases is the importance of human behavior. The cessation of unhealthy patterns of behavior and the acquisition of healthy patterns are critical for primary and secondary prevention and for many treatments. The transtheoretical model is an integrative model of behavior change that can provide the conceptual basis for developing interventions to modify a problem behavior or to acquire a positive behavior. The central organizing construct of the model is the stages of change. The model also includes a series of independent variables (the processes of change) and a series of outcome measures, including the Decisional Balance and the Temptation scales. The application of the model to smoking cessation and stress management is illustrated. (PsycINFO Database Record (c) 2012 APA, all rights reserved)