Advances an evolution-based model of strategic conflict between men and women. Conflict is predicted to occur whenever the reproductive strategy adopted by one sex interferes with that adopted by the opposite sex. Three empirical studies tested hypotheses based on this model. Study 1 (N = 528) examined sex differences in sources of anger and upset (e.g., about sexual aggressiveness or withholding) among 2 samples of Ss differing in age and martial status. Study 2 (N = 60) assessed the perceived magnitude of upset each sex would experience when confronted by each source. Study 3 (N = 214) tested predictions within married couples about sex differences in sources of marital and sexual dissatisfaction. These studies provide modest support for the strategic conflict model and implicate the negative emotions of anger and upset as proximate mechanisms that alert men and women to strategic interference. The diversity of upset elicitors discovered here, such as being condescending, possessive, neglecting, abusive, inconsiderate, moody, and self-centered, point to the limitations of this evolutionary model and the need to develop more comprehensive models of conflict between the sexes.