Ten Type A's and 10 Type B's, as measured by the student version of the JAS and the TASRI, exercised on a cycle ergometer for 20 minutes at light (40% V02max), moderate (60% V02max), and high (80% V02max) intensity exercise to determine A/B differences in psychophysiological responses. The norepinephrine and epinephrine responses of A/B types were similar at the light and moderate intensities. However, at the high intensity, norepmephrine response of Type A's was significantly greater than that of Type B's. Epinephrine responses (p=.ll) evidenced the same, albeit nonsignificant, trend. Oxygen uptake and heart rate data indicated that this amine difference was not a function of differential workloads, suggesting that Type A's had a greater psychophysiological reactivity to high intensity exercise than Type B's. Ratings of perceived exertion were similar for Type A's and B's at all intensities. However, a significant interaction between behavioral pattern and intensity emerged for affect. Interpretation of this interaction indicated that Type A's were more positive than B's at light and moderate intensities, yet at the high intensity exercise A's were more negative than B's. The results of this study suggest that A and B types do differ in their psychophysiological responses during exercise, with A's evidencing more positive affect during light and moderate intensities, yet more negative affect and greater neuroendocrine responses during high intensity exercise than B's.