This study examined the relationship of preexisting efficacy for exercise with perceptions of effort expenditure and in-task affect during exercise testing. Subjects comprised sedentary, middle-aged adults participating in a submaxi-mal cycle ergometer-graded exercise test. Perceptions of efficacy were assessed prior to and following exercise testing while perceptions of effort expenditure and in-task affect were assessed at 70% of predicted maxim heart rate. Highly efficacious subjects had lower perceptions of effort expenditure and reported more positive affect during exercise than did their less efficacious counterparts. Affective responses during exercise were in turn significant predictors of posttest self-efficacy. These results are discussed in regard to the importance of examining the role of personal efficacy in the formation of exercise-related affect and affective responses as sources of efficacy or competence information in exercise.