Economics and business students regularly behave less prosocially than others. Can ethics training reverse this tendency? Results from a repeated public goods experiment reveal that it can. Students who attend an interactive lecture on social dilemmas show significantly more cooperation than others. However, the lecture does not appear to increase the incidence of reciprocal behavior. As many current social problems qualify as social dilemmas, this result stresses the importance of ethics training for policy makers and curriculum designers alike in overcoming the incentive structure of social dilemmas.