Evolutionary theory based research shows that women and men may differ in their responses to sexual and emotional infidelity. The present research sought to determine how the mate value characteristics of rivals affect the levels of emotional reaction men and women experience with these types of infidelity. Women were expected to report higher levels of upset when their male partners committed infidelity with an attractive rather than an unattractive woman while men were expected to experience the most upset when their female partners committed sexual infidelity with a male rival regardless of the rival's financial status. The results were partially consistent with these hypotheses. Women were most upset by their partner's sexual infidelity regardless of the attractiveness of their female rival and more upset by their partner's emotional infidelity with an attractive woman. Men were most upset with their partner's commission of sexual infidelity regardless of the financial status of their male rival. These findings are discussed in terms of prior research examining sex differences in jealousy and intrasexual competition.