More than 200 studies have found “gender symmetry” in perpetration of violence against a marital or dating partner in the sense that about the same percent of women as men physically assault a marital or dating partner. Most of these studies obtained the data using the Conflict Tactics Scales (CTS). However, these results have been challenged by numerous articles in the past 25 years that have asserted that the CTS is invalid. This article identifies and responds to 11 purported methodological problems of the CTS, and two other bases for the belief that the CTS is not valid. The discussion argues that the repeated assertion over the past 25 years that the CTS is invalid is not primarily about methodology. Rather it is primarily about theories and values concerning the results of research showing gender symmetry in perpetration. According to the prevailing “patriarchal dominance” theory, these results cannot be true and therefore the CTS must be invalid. The conclusion suggests that an essential part of the effort to prevent and treat violence against women and by women requires taking into account the dyadic nature of partner violence through use of instruments such as the CTS that measure violence by both partners. Copyright © 2012 John Wiley & Sons, Ltd.