The special vulnerability of individuals to loss or separation may result in precipitation not only of emotional but of somatic disorders. Material from the study of psychosomatic, psychotic, and borderline patients is used to show how the interrelationship between the individual and his environment can be expressed in both health and disease by either mental or physical activity. The problem is approached through study of sensory perception, internalized symbolization, and extension of Freud's theory of conversion and their relationship to personality and body image development.