This study tested the hypothesis that the Type A behavior pattern and its 
components are associated with increased activity of the sympathetic nervous 
system. To do this, we employed two new markers of sympathetic tone--pupil size 
and platelet catecholamine content. Thirty-three healthy males were blindly 
rated for Type A behavior and verbal stylistic components by Structured 
Interview. Adrenergic tone to the pupils was assessed from pupil diameter 
recorded by infrared television pupillometry, and pupil alpha-adrenergic 
sensitivity was estimated from mydriatic response to ophthalmic phenylephrine. 
Platelet epinephrine and norepinephrine contents were assayed because these 
levels are associated with chronic, long-term circulating catecholamine levels. 
The results showed Type As had consistently larger pupil diameters than Type Bs 
(p = 0.03, 0.03, and 0.01). There was no difference in pupillary response to 
phenylephrine instillation between groups. Platelet epinephrine content was 
greater in Type A subjects (chi 2 = 4.25, p less than 0.04, t = 1.6, p = 0.06). 
Only the component of explosiveness was modestly associated with resting pupil 
size, and no components significantly predicted platelet catecholamines. We 
conclude that the results of these two new markers of autonomic activity, 
namely, pupil size and platelet epinephrine, suggest that Type A behavior is 
characterized by increased sympathetic nervous system tone although we cannot 
rule out the possibility of decreased activity of the parasympathetic nervous 
system.