No single theory dominates research or practice (Glantz et al., 1990). Theories explain or predict future actions. Theories tell us about the what, how, when, and why and help in the selection of appropriate interventions and the implementation of educational programs (Glantz et al., 1990). This section will outline a variety of theories that are applicable to behavioral medicine such as: Behavioral Medicine Paradigm, Theory of Reasoned Action, Multi-attribute Utility Theory, Attribution Theory, Consumer Information Processing, Social Learning Theory, and Trans-theoretical Model.