The authors investigated whether students who selectively volunteer for a study of prison life possess dispositions associated with behaving abusively. Students were recruited for a psychological study of prison life using a virtually identical newspaper ad as used in the Stanford Prison Experiment (SPE; Haney, Banks & Zimbardo, 1973) or for a psychological study, an identical ad minus the words of prison life. Volunteers for the prison study scored significantly higher on measures of the abuse-related dispositions of aggressiveness, authoritarianism, Machiavellianism, narcissism, and social dominance and lower on empathy and altruism, two qualities inversely related to aggressive abuse. Although implications for the SPE remain a matter of conjecture, an interpretation in terms of person-situation interactionism rather than a strict situationist account is indicated by these findings. Implications for interpreting the abusiveness of American military guards at Abu Ghraib Prison also are discussed.