Surveys of married and dating couples find that women assault their male partners at about the same rate as men assault female partners. When assaults serious enough to cause death were examined, it was found that in contrast to the extreme rarity of homicide by women outside the family, women kill their male partners at a rate that approaches the rate at which men kill their female partners. These findings based on family survey data and homicide data are in marked contrast to the findings from studies using data produced in the context of the criminal justice system on non-lethal assaults. The criminal justice data yield low rates of domestic assault by men, and even lower rates of domestic assault by women. The criminal justice data are so low because those rates are based on differential definitions of the appropriateness of reporting incidents to the police or to a National Crime Survey interviewer. Most domestic assaults by men, and almost all domestic assaults by women are filtered out because there is no injury and the victim therefore does not consider them a "real crime." In addition, the rates for women are particularly low because both male victims and the police may be especially reluctant to invoke the criminal justice system against women who assault their husbands. However, women produce less injury than do men. Domestic assaults by women need to be added to efforts to prevent assaults on women due to the moral wrongness of the act, the modeling of assaultive behavior, and to reduce the danger to women themselves. Further research is needed on gender differences in the objectives, meaning, and consequences of domestic assaults. (ABL)