Anxiety is the psychophysiologic signal that the stress response has been initiated. The stress response's by-product, stress, is difficult to define. The response has multiple dimensions that have yielded research with many foci. Most salient to nursing are investigations of psychobiologic variables, the influence of life events, and the interactional model of the stress response. The stress response can be viewed as an interactional process that causes psychophysiologic reactions that are immediate and can occur up to and including physiologic events 3 weeks after confrontation with the stressor. The literature suggests that neuroendocrine alterations in response to confrontation with a stressor may influence immunocompetence. Intervention and prevention studies of stress focus on pharmacotherapy, psychotherapy, behavioral techniques, personality engineering, relaxation training, and biofeedback. Nursing research on stress has proliferated in the 1980s. Implications for nursing intervention include coping strategies that fall into four categories: behavioral, physical, cognitive, and emotional.