Two studies explored the influence of aerobic fitness level on autonomic reactivity to psychosocial stress. Experiment 1 employed a correlational, repeated measures design. A total of 45 men who were physically trained, untrained, or training were tested at three-week intervals over nine weeks. The measure of autonomic reactivity was lability in electrodermal activity during two speeded mental tasks designed to induce psychosocial stress. In the initial test session, trained subjects showed faster autonomic recovery from this stress than did untrained or training subjects; in subsequent test sessions involving the repeated administration of the same tasks, the three groups were indistinguishable. Experiment 2 employed 60 subjects who were randomly assigned to 10-week aerobic exercise, meditation, or music appreciation programs. In each session, two psychosocial stressors selected from a battery of six tasks were counterbalanced across treatments and sessions. Over the course of the study, participants in the exercise program improved significantly in physical fitness and also showed faster recovery in the electrodermal response. This quicker autonomic recovery may allow the aerobically fit to cope more effectively with emotional stress.