IOFEEDBACK is “the use of modern instrumentation to give an individual better moment-to-moment information about a physiologic process that is under the control of the nervous system but not clearly or accurately perceived.“’ Such information can be used to learn the regulation of these processes (e.g., blood pressure) and in fact, biofeedback approaches are now being applied to the treatment of a wide variety of disorders in which physiologic responses are deranged (e.g., hypertension). Relaxation training is often combined with biofeedback procedures in such treatment. This training can produce a relaxation response* or low arousal state3 characterized by decreased oxygen consumption, heart rate, blood pressure, muscle tone, and respiratory rate as well as increased skin resistance and alpha and theta activity.2 Some investigators have suggested that cultivating a relaxed state alone is a useful technique for treating medical problems. 4s The clinical application of relaxation and biofeedback has been given a great deal of publicity that is optimistic in nature, but too few critical reviews of evidence.=s’ None of these reviews have focused on the treatment of the disorders most frequently referred to psychiatrists-those in which psychologic factors are usually considered to be important; i.e., psychosomatic and functional conditions. Since biofeedback may provide a new alternative or adjunctive therapy to the psychiatrist, this author will review research on the clinical application of biofeedback, alone or in combination with relaxation, to psychosomatic or functional disorders. These include anxiety states, phobias, headaches, insomnia, functional bowel disturbances, Raynaud’s phenomenon, and hypertension. By examining research performed on patients, I will present a status report on the use of biofeedback for each clinical problem. In this way I hope to present a realistic picture of the present value of this treatment approach for the clinical psychiatrist. Anxiety States (Table I) Raskin et al.’ treated 10 chronically anxious patients who had had prior treatment with psychotherapy, and in some instances tranquilizers, without clinical benefit. Before active treatment was begun, an 8-wk baseline period was used to assess symptoms and practice relaxation at home. Subsequently, 40 electromyogram (EMG) feedback sessions were given over an 8-wk period, while home relaxation was encouraged. No treatment control groups were established. Results showed four patients with at least moderate relief of symptoms. Most other subjects were unable to affect symptoms but could relax in a calm environment. Gar