Poverty or patriarchy, alcohol or aggression; the causes of intimate partner violence have been contested by social scientists for decades. Underlying the controversy is an inescapable problem: evidence for causation of intimate partner violence is weak when assessed with epidemiological criteria.1 Most research has been from North America and, with some exceptions,2 and 3 has been based on women accessing sources of help, with data obtained from shelters, official records, or clinic samples.4, 5 and 6 However, during the past decade, the research base has been expanded substantially by several well designed cross-sectional studies of violence against women from developing countries, which focus on both women7, 8 and 9 and men,6, 10 and 11 and by ethnographic studies.12 and 13 This increase in data has enabled researchers to identify associations that pertain to more than one setting, explore hypotheses critically, and understand the plausibility of associations when considered in the light of what else is known about a society. Furthermore, understanding of the mechanisms through which many associated factors contribute to intimate partner violence has been greatly advanced, helping clarify interventions needed for primary prevention.