The paper reports results from analyses of the physical aggression against dating partners by four samples of university students in Ciudad Juarez, Mexico, Mexican Americans and Non-Mexican Whites in El Paso and Lubbock Texas, and New Hampshire (N=1,544). The percent reporting partner violence (PV) was high in all samples, but also differed significantly between samples. The lowest rate was in New Hampshire (29.7%), followed by Texas, Non-Mexican Whites (30.9%), Texas Mexican American (34.2%), and the highest rate was in Juarez (46.1%). When only severe assaults were compared, the differences between samples was similar, i.e., lowest in New Hampshire and highest in Juarez. In all four samples, there was no significant difference between males and females in either the overall prevalence of physical aggression or the prevalence of severe attacks. Among the 553 couples where one or both of the partners were violent, in almost three quarters of the cases (71.2%) there was gender symmetry in the sense that both partners engaged in this type of behavior. When only one partner was violent, this was twice as likely to be the female partner (19.0%) as the male partner (9.8%). Among the 205 couples where there was an act of severe aggression, symmetry was less prevalent (56.6%), but when only one partner was violent, it was again twice as likely to be the female partner (29.8% female only versus 13.7 male partner only). These results are consistent with the gender symmetry in PV found in many studies. They extend those results by showing that gender symmetry prevails in four different cultural contexts. The presence of gender symmetry in these different cultural contexts, combined with studies showing that women are injured more often and more seriously by partner-assaults, and studies showing that women initiate PV as often as men, suggests that programs and policies aimed at primary prevention of PV by women are crucial to ending PV and for reducing the victimization of men and women. Aggr. Behav. 33:281–290, 2007. © 2007 Wiley-Liss, Inc.