This paper reviews biofeedback research from the perspective of cybernetic/feedback theory and applies the theory to the behavioral treatment of psychosomatic disorders. The concept of disregulation is used to elucidate how environmental factors can modulate the central nervous system and effect homeostatic, self-regulatory control of peripheral organs. When feedback from peripheral organs is disrupted, it is hypothesized that disregulation occurs, leading to physiological instability and functional disease. Within this framework, biofeedback provides a new feedback loop that can help individuals regain physiological self-control. Basic research using biofeedback to enhance self-regulation of cardiovascular responses is reviewed. The use of biofeedback in the behavioral treatment of disorders such as tension and migraine headache, hypertension, and epilepsy are selectively reviewed and critically evaluated. The need to consider feedback mechanisms in behavioral and biomedical approaches to treatment is highlighted. Predictions regarding the potential inadvertent perpetuation of disregulation and disease through inappropriate biomedical intervention is also considered.