THE IMPORTANCE of the psychological stress response makes necessary a detailed knowledge of its psychological and physiological properties. Because of the well-known difficulties of research in natural settings, a number of laboratory approaches have utilized artificial stimuli to produce what is thought to be psychological stress. Relatively simple sensory stimuli (eg, sound) or intellectually demanding tasks (eg, mental arithmetic) often are so used. Such stimuli can be well defined in terms of their physical parameters; they are easy to produce; they have a sharply delimited onset and termination; and they can be brief in duration. This affords much greater simplicity of experimental design as well as uniformity for repetition. Simple stimuli, however, lack the quality of threat and the capacity to produce overt affective arousal. Clinically oriented investigators have tended to prefer the use of more complex stimuli which have qualities more like meaningful real-life psychological stress situations (eg, anxiety-inducing