University oj OxfordAll available studies concerning desensitization and utilizing psychophysiological measurement are reviewed and evaluated. Autonomic changes, particularly in heart rate and skin resistance, do occur following desensitization, and this treatment seems a relatively effective method of modifying such physiological components of fear. The reported effects of phobic imagery are consistently different from those of neutral imagery and show a characteristic response decrement with repetition, although the role played by relaxation in facilitating this decrement remains unclear. Partial dissociation between physiological and other behavioral changes in treatment appears frequently, and may be attributed to varying rates of change in the different systems. Some theoretical accounts of the mechanisms involved in desensitization are discussed in light of the evidence reviewed.