This study investigated the relationship between the Type A coronary-prone behavior pattern and the sympathetic nervous system arousal elicited during challenge. Type A and B (noncoronary-prone) subjects were randomly assigned to a task whose instructions indicated that the task was either Easy or Hard (Subjective) and which was in fact either Easy or Hard (Objective). Type B's became physiologically aroused only when they encountered a hard task that they were expecting to be hard. Type A's, on the other hand, became physiologically aroused both when the task was hard and also when they expected it to be hard. This latter effect was present even when the task was in fact easy. The results were discussed in terms of specific Type A behavior, as well as a more general illness behavior.