Since psychoimmunology is now 10 to 20 years of age, it seems appropriate to expect a certain maturity in the field. It seems reasonably well established that there really is neuroimmunomodulation. The biological and medical importance of this is the possible influence of psychological factors on immune competence. Inasmuch as it is reasonably well established that psychological factors do have such an influence, the field must now endeavor to establish how important this influence is. It no longer suffices to show that some sort of stressor has some sort of action on some part of the immune cascade of responses. "Stressors" do not act indiscriminately; they are filtered and interpreted by the brain following psychological principles that again are reasonably well known. The distinction between "stress" and "distress" is important for the health consequences of how and with what success an individual is handling a stressful situation. Concepts such as coping, control, helplessness, and hopelessness are required to understand how immune responses are influenced by the brain and to establish the extent to which these mechanisms have clinical validity in man and animals.