The influence on social behavior of beliefs in Satan and the nature of evil has received little empirical study. Elaine Pagels (1995) in her book, The Origin of Satan, argued that Christians' intolerance toward others is due to their belief in an active Satan. In this study, more than 200 college undergraduates completed the Manitoba Prejudice Scale and the Attitudes Toward Homosexuals Scale (B. Altemeyer, 1988), as well as the Belief in an Active Satan Scale, developed by the authors. The Belief in an Active Satan Scale demonstrated good internal consistency and temporal stability. Correlational analyses revealed that for the female participants, belief in an active Satan was directly related to intolerance toward lesbians and gay men and intolerance toward ethnic minorities. For the male participants, belief in an active Satan was directly related to intolerance toward lesbians and gay men but was not significantly related to intolerance toward ethnic minorities. Results of this research showed that it is possible to meaningfully measure belief in an active Satan and that such beliefs may encourage intolerance toward others.