BACKGROUND: Violence against women is a serious human rights abuse and public health issue. Despite growing evidence of the size of the problem, current evidence comes largely from industrialised settings, and methodological differences limit the extent to which comparisons can be made between studies. We aimed to estimate the extent of physical and sexual intimate partner violence against women in 15 sites in ten countries: Bangladesh, Brazil, Ethiopia, Japan, Namibia, Peru, Samoa, Serbia and Montenegro, Thailand, and the United Republic of Tanzania. METHODS: Standardised population-based household surveys were done between 2000 and 2003. Women aged 15-49 years were interviewed and those who had ever had a male partner were asked in private about their experiences of physically and sexually violent and emotionally abusive acts. FINDINGS: 24,097 women completed interviews, with around 1500 interviews per site. The reported lifetime prevalence of physical or sexual partner violence, or both, varied from 15% to 71%, with two sites having a prevalence of less than 25%, seven between 25% and 50%, and six between 50% and 75%. Between 4% and 54% of respondents reported physical or sexual partner violence, or both, in the past year. Men who were more controlling were more likely to be violent against their partners. In all but one setting women were at far greater risk of physical or sexual violence by a partner than from violence by other people. INTERPRETATION: The findings confirm that physical and sexual partner violence against women is widespread. The variation in prevalence within and between settings highlights that this violence in not inevitable, and must be addressed.