The transtheoretical model of behavior change postulates five distinct, well-defined stages of change: Precontemplation, Contemplation, Preparation, Action, and Maintenance. Each stage has been regarded as reflecting a motivational posture and treated as if it is homogenous with respect to membership. This paper reports the results of four cluster analytic studies, one within each of the first four stages of change. The cluster analysis was based on three constructs of the model. Four distinct subtypes were found within Contemplation, Preparation, and Action, and three subtypes were found within Precontemplation. External validation for the clusters was provided using the 10 Processes of Change and 8 behavioral measures as dependent measures. At least one subtype corresponded to the existing stage definition but the other subtypes suggested alternative intervention strategies.