Contemporary psychosomatic medicine must take into consideration developments in psychobiology. The difficulty in accepting dualistic concepts is a serious challenge to positions distinguishing between psychological and 'real' causes of disease. There is more emphasis on life style factors for disease and on the impact of psychosocial factors on illness rather than on disease. The neurophysiological concept of activation or arousal has been important in the development of rational pathophysiological models that describe how sustained arousal may be a pathophysiological factor. For illness, sensitization may be an acceptable psychobiological mechanism underlying very frequently occurring and expensive medical conditions that require medical and economical assistance. One possible alternative to old dynamic concepts is the development of a cognitive arousal theory of stress.