Environmentally induced stereotypies in gestating sows were inhibited by haloperidol. This inhibitory effect was stronger in sows that directed stereotyped activities toward objects in the environment than in sows performing self-directed stereotypies. The results indicate that dopamine is involved in the performance of stereotypies in pigs, and that haloperidol seem to impair motivational arousal primarily by reducing the rewarding impact of stereotyped self-stimulation.