Twenty male college students and 20 male prisoners of comparable age were first angered by a confederate of the E and then permitted to aggress against this individual by means of electric shock. Before agressing, half of the Ss in each of these two groups were exposed to the behavior of an aggressive model, while the remaining individuals attacked the anger instigator in the absence of such experience. Results indicated that the prisoners delivered significantly more intense shocks to the victim than did the students. In addition, exposure to the model was highly effective in raising the level of aggression on the part of Ss in both groups. These results were discussed in terms of the evidence they provide for the validity of laboratory techniques for the study of human aggression.