Studies investigating the events that elicit men's and women's jealousy consistently show that men's jealousy, more than women's jealousy, is triggered by a mate's sexual infidelity, and women's jealousy, more than men's jealousy, is triggered by a mate's emotional infidelity. Internet infidelity poses new challenges for modern couples. Therefore, the present study investigated men's and women's responses to emotional and sexual infidelity over the Internet. Results from both a student sample (n = 254), and a sample from the general population (n = 483) showed that sex differences in response to Internet infidelity parallels those for offline infidelity. Implications and explanations for this finding, as well as different results between both samples, are discussed.