This paper uses multivariate logistic regressions to explore: (1) potential socio-economic, cultural, psychological and political determinants of AIDS conspiracy beliefs among young adults in Cape Town; and (2) whether these beliefs matter for unsafe sex. Membership of a religious organisation reduced the odds of believing AIDS origin conspiracy theories by more than a third, whereas serious psychological distress more than doubled it and belief in witchcraft tripled the odds among Africans. Political factors mattered, but in ways that differed by gender. Tertiary education and relatively high household income reduced the odds of believing AIDS conspiracies for African women (but not men) and trust in President Mbeki's health minister (relative to her successor) increased the odds sevenfold for African men (but not women). Never having heard of the Treatment Action Campaign (TAC), the pro-science activist group that opposed Mbeki on AIDS, tripled the odds of believing AIDS conspiracies for African women (but not men). Controlling for demographic, attitudinal and relationship variables, the odds of using a condom were halved amongst female African AIDS conspiracy believers, whereas for African men, never having heard of TAC and holding AIDS denialist beliefs were the key determinants of unsafe sex.