conflict and displacement; for example, rape is often used as a weapon of war, and refugee settings often involve a high degree of violence and insecurity (Ward, 2002).

To limit the scope of this review, this paper will focus on the two most common forms of gender-based violence: intimate partner violence (physical and sexual) and sexual violence by any perpetrator. As a starting point, the World Report on Violence and Health (Krug et al., 2002) offered the following definitions of intimate partner violence and sexual violence, respectively:

**_Intimate partner violence:_** Any behavior within an intimate relationship that causes physical, psychological or sexual harm  . . . Such behavior includes:

- Acts of physical aggression-such as slapping, hitting, kicking and beating

- Psychological abuse-such as intimidation, constant belittling and humiliating

- Forced intercourse and other forms of sexual coercion

- Various controlling behaviors-such as isolating a person from their family and friends, monitoring their movement and restricting their access to information or assistance (Heise and Garcia Moreno, 2002, page 89).

**_Sexual violence:_** Any sexual act, attempt to obtain a sexual act, unwanted sexual comments or advances  . . . using coercion, by any person regardless of their relationship to the victim, in any setting, including but not limited to home and work...Sexual violence includes rape, defined as physically forced or otherwise coerced penetration...of the vulva or anus, using a penis or other body parts or an object.  Sexual violence can include other forms of assault involving a sexual organ, including coerced contact between the mouth and penis, vulva or anus (Jewkes, Sen and Garcia Moreno, 2002, page 149).

# **MAGNITUDE AND DYNAMICS**

Measuring levels of violence against women poses many challenges. Estimates vary depending upon how researchers define violence, the questions they ask, the timeframes they explore, and the sample characteristics. Heterogeneous approaches often make it difficult to compare research findings. Another challenge is that surveys are best at measuring discrete incidents of physical violence; rather than the pattern of controlling, violent behavior often referred to as “battering”, which is typically characterized by multiple forms of abuse--physical, emotional, sexual, etc. (Ellsberg et al., 2001a). Such violence often escalates with time and involves a high level of fear among women for their safety and lives.

Sexual violence poses its own definition and measurement challenges. For one thing, sexual violence encompasses a large range of manifestations (from verbal harassment, to unwanted touch, molestation, assault and penetration), settings, and perpetrators. Jewkes (2002) developed a framework for understanding different types of sexual violence against women, ranging from the most visible, namely fatal sexual assault and rape reported to the police, to the most common form and least visible forms of sexual violence that occur within marriage, dating relationships and families. Theoretical and methodological approaches to research on sexual abuse/violence are even more diverse than those focused on intimate partner violence. Typically, researchers use different study designs to measure levels and patterns of child sexual abuse, forced sexual initiation during adolescence, rape among the general population of women, forced sex within marriage, and sexual harassment / abuse within schools.

A serious challenge for all types of research on the prevalence of gender-based violence is that most estimates probably reflect a certain degree of under-reporting. Women are often reluctant to disclose experiences of physical or sexual violence due to shame or fear of reprisals (Koss, 1993). Underreporting appears to be particularly problematic in large-scale surveys designed primarily for other purposes, such 9