The article summarizes the literature on the etiological significance of psychologic factors in allergic diseases. Records of 100 consecutive cases of the following 6 common allergic syndromes were reviewed: ragweed hayfever, extrinsic asthma, atopic eczema, perennial vasomotor rhinitis, "intrinsic" asthma and chronic urticaria. In the first 2 groups all patients gave positive skin tests." The therapeutic results of specific avoidance or immunization were highly successful for these groups. Patients suffering from atopic eczema did not consistently give positive skin tests, and negative skin tests were characteristic of patients in the last 3 groups. Furthermore, in the latter 3 groups the patients'' response to allergic and other methods of therapy was generally unsatisfactory as well as being uncertain and unpredictable. These groups were made up more predominantly of women. The individuals tended to suffer from multiple complaints and showed many factors characteristic of psychologic maladjustment. They showed improvement when treated by psychologic methods.