The present study investigated perceived descriptive norms (i.e., perceived prevalence) for male-to-female intimate partner violence (IPV) following victim infidelity (i.e., girlfriend had sex with another man). While watching a video-taped vignette of a young, dating couple in an argument that escalated to male-to-female violence, male participants were asked various questions to assess perceived descriptive norms at several time points during the escalating argument. Half of the participants were told that the victim in the video was unfaithful. Results suggested that while participants did believe that it was much more common for their male friends and for typical male students to aggress against unfaithful girlfriends compared to faithful girlfriends, these differences were less pronounced as the aggression intensified. When testing whether perceived norms for IPV were related to participants' purported risk of engaging in IPV, a clear pattern appeared: For the no-infidelity condition, IPV perceived norms for male friends and perceived norms for typical male students were each significantly related to participants' likelihood of engaging in IPV, such that the higher the estimated norm, the higher the participants' risk. However, for the infidelity condition, only perceived norms for male friends were related to the risk of engaging in IPV. Findings have important implications for social norms-based intervention and prevention programs for IPV on college campuses. (Contains 1 table and 2 figures.)