Both Dweck (1986) and Nicholls (1984) proposed that when ego-involved individuals encounter difficulty, they would begin to doubt their level of ability, and as a consequence, their commitment to the goal of demonstrating high ability would decline. As difficulty continued, perceived ability would decline, and eventually the goal would be abandoned. In the present study, the authors tested these predictions utilizing a longitudinal experimental design to assess changes across time in students' perceived ability, achievement goals, performance, and affective reactions as they experienced differing levels of task difficulty in an ego-involving context. College students (N = 156) participated in 3 sessions, each 1 week apart, in which they were given ego-involving instructions and worked on "intelligence test" items. While the average level of difficulty of the session increased progressively in the experimental condition, it remained similar across sessions for the control condition. Results were generally supportive of the original predictions. As the difficulty of the items increased across sessions, students' perceived ability declined and so did their commitment to performance-approach goals, while their endorsement of work-avoidance goals increased. Also consistent with predictions, students experiencing increasing difficulty expressed stronger escapist thoughts, more negative affect, and less positive affect. (Contains 1 footnote, 8 tables, and 8 figures.)