Objective: Evolutionary models posit that jealousy is a sexually dimorphic phenomenon: men worry most about a partner’s sexual infidelity and women worry most about emotional infidelity. Social cognitive models emphasize that the presence and size of sex differences varies between and within cultures. Our aim was to examine how sex and other variables affected responses to a hypothetical jealousyevoking scenario. Design and Method: Computer-assisted telephone interviews were completed by a population-representative sample of 20,094 Australians aged 16-69. Analyses focused on responses to the question ‘What would distress you more: imagining your partner forming a deep emotional attachment to another person, or having sexual intercourse with another person?’ Results: Among heterosexual respondents, men were most likely to report that they would be most distressed by their partner’s sexual infidelity, and women were also most likely to report that they would be most distressed by their partner’s emotional infidelity, but only among women aged 20-49 did a majority report that emotional infidelity would be most distressing. Among bisexual and homosexual respondents, most women and men reported that they would be more distressed by emotional infidelity, and men were more likely than women to choose this option. Among all groups, responses were also significantly related to sexually liberal attitudes. Conclusions: The results provide some support for evolutionary models of jealousy, but highlight the importance of considering how responses to jealousy-evoking scenarios are affected by age, sexuality, and attitudes.