The role that the client's cognitions (viz., his self-statements and images) play in each of the various phases of biofeedback training is examined. Biofeedback training is conceptualized as including three phases: initial conceptualization, skills-acquisition and -rehearsal, and transfer of treatment. Cognitive-behavior modification procedures to alter or employ the clients' cognitions at each of these phases of treatment are described. A cognitive theory of self-control is offered, postulating a three-stage mediational change process whereby: (1) the client must become an observer of his behavior and physiological responses; (2) this recognition becomes the cue to emit incompatible cognitions and behaviors; and, finally, (3) the content of the client's cognitions following change influences the generalization and persistence of treatment effects. The implications of this theory for biofeedback training are discussed.