Introduction. Research shows that in most situations, women perceive themselves to be at greater risk of harm than do men. Gustafson's gender role perspective on risk perception suggests that this is because women are socialized to feel that they need protection, especially from men. Aims. Based on Gustafson's gender role perspective on sex differences in risk perception, we predicted that in at least one context, perception of romantic partners' sexual risk, this gender difference would be reversed. Specifically, women should rate boyfriends as having lower risk for sexually transmitted infections (STIs) than boyfriends rate themselves having. Methods. In two studies, we examined heterosexual couples and compared women's perceptions of their boyfriends' sexual risk level with the boyfriend's self-perception of sexual risk. Main Outcome Measures. Self-reported measures of risk for STIs, perception of romantic partners' risk for STIs. Results. On multiple measures, women rated their boyfriends as having a lower risk for STIs than the men rated themselves. Men did not show this pattern and, in some cases, showed the reverse pattern of perceiving their girlfriends to have a greater level of risk than girlfriends themselves believed they had. Conclusions. Consistent with Gustafson's gender role perspective on risk perception, heterosexual women perceived their romantic partners as relatively less risky in terms of STI risk than men perceived themselves. One potential implication of this finding is that women may be less likely to protect themselves against disease in close romantic relationships because they believe that their partners are low risk, regardless of the partners' actual risk levels. Conley TD, and Peplau LA. Gender and perceptions of romantic partners' sexual risk. J Sex Med 2010;7:794-802.