The present research addresses the question of whether avoidant control that is difficult to exercise induces greater physiologic arousal and unpleasant affect than easy-avoidant control or no-avoidant control. Two types of control difficulty were distinguished and factorially varied: (a) control difficulty due to the effortfulness of a controlling activity and (b) control difficulty due to uncertainty about how to exercise control over an unpleasant outcome. To examine responses under conditions where avoiding an unpleasant event is impossible, a cell was included in which subjects were not given the means by which to exercise control. In all but one condition (the high-effort-exercise/high-response-uncertainty condition), when avoidance was expected to be easy or impossible (a) pulse rates were lower, (b) digital pulse volumes were higher (indicating reduced physiologic activity), (c) self-reported anxiety was lower, and (d) ratings of the stressor's unpleasantness were lower than they were when avoidance was expected to be difficult. In the high-effort-exercise/high-response-uncertainty condition, cardiovascular arousal, self-reported anxiety, and shock unpleasantness scores were relatively low, suggesting that control was sufficiently difficult in that condition to cause subjects to "give up." Results are discussed in terms of a recently proposed model of motivation, conceptions of anxiety, and the relation between stress and control.