The transtheoretical model of health behavior change is described and supporting empirical work is presented that reviews the central constructs of the model: the stages of change, processes of change, decisional balance, confidence, and temptation. Model-based applications to a broad range of problem behaviors are summarized. Applications to human immunodeficiency virus (HIV) prevention behavior changes are highlighted for each variable. Finally, several questions about the area of sexual behavior change to reduce risk of HIV exposure are explored and future research ideas are described within the context of this model.