The present paper sought to clarify the conceptual relationship between expectancy for personal control, stress, and behavioral reactions to stress. Expectancy for control was assessed as a personality characteristic of internal control; stress was experienced as strong environmental interruptions, disturbances and unpredictable obstacles encountered during the performance of assigned tasks. Subjects were junior high school aged students who attempted to complete three academic type tasks during one of two levels of stress or a base line, no stress, condition. Analyses of the data included: (a) internal subjects were capable of sustaining task performance under high stress, but external students experienced performance decrements as stress increased; (b) time to complete the mathematics task reflected a facilitating effect of stress for internals but a debilitating effect for externals; (c) performance differences between internal and external students, in the absence of differences in reported anxiety, could be attributed to the stronger reward expectancies possessed by the internal individual. Interpretation of the data suggested an interactive relationship between type of stress (threat to ego vs. threat to instrumental performance) and expectancy for control in the influencing of behavior reactions to stress.