On their third date, Michael takes a woman to an expensive restaurant. Afterwards she invites him to her apartment. They kiss and touch each other. She asks him to wear a condom if they are going to have sexual relations. He refuses. She says "no." He continues to touch her intimately, seducing her beyond where she wants to go.

Susan's long-term partner wants to have sex with her but she is angry with him about something and doesn't want to be intimate. He persists, forcing himself upon her.

Marsha's husband has been drinking. He grabs her, takes her into the bedroom and makes her have sex.

Each of these incidents is an example of acquaintance or date rape. So exactly what does the term mean? "Hidden rape," as it is sometimes called, refers to sexual violence where the victim knows the rapist. It occurs when someone familiar - friend, relative, co-worker, boyfriend, husband - forces or coerces another person to have sex. Date rape is not exclusively perpetrated by men against women, but women are subject to dating violence at least twice as often as men and boys. One study found that women were six times more likely than men were to experience violence at the hands of an intimate partner. Women also suffer significantly more injuries than men do.

Since the 1980s, acquaintance rape has been recognized as a serious problem in the U.S. Scholarly research coupled with personal memoirs and a plethora of public cases charging acquaintance rape galvanized public attention. Subsequent legal decisions have been handed down in which definitions of rape were clarified and such issues as "menace" and "duress" were examined. The definition of "consent" was expanded to mean "positive cooperation in act or attitude pursuant to an exercise of free will." The courts determined that "a person must act freely and voluntarily and have knowledge of the nature of the act or transaction involved."

Now, the problem of acquaintance rape is drawing new attention because of emerging data on teen dating violence. According to the National Teen Dating Violence Prevention Initiative, teens are at greater risk than adults are for intimate partner violence. Young women between 10 and 24 years of age are more vulnerable to such violence than any other age group, at rates nearly tripling the national average. About one-in-five female high school students report being physically and/or sexually abused by a dating partner, and 58 per cent of rape victims report being raped between the ages of 12 and 24.

Both before and after high school, girls are likely to be victims of violence from someone they know. One study revealed that among female and male eighth and ninth graders, 25 per cent had been victims of non-sexual dating violence and eight per cent had been victims of sexual dating violence. On the other end of the spectrum, a national study of college students found that 27.5 per cent of women surveyed said they had suffered date rape or attempted rape at least once since the age of 14.

Only five per cent of those experiences were reported to the police, a figure much lower than reported rapes when the perpetrator is a stranger. Experts suggest that the reasons for under-reporting of date rape range from self-blame to guilt to fear of being held responsible. According to The American Academy of Experts in Traumatic Stress (AAETS), women and girls often confide in a friend about their experience but resist going to authorities. They say girls fear the reaction of family and friends if the victim has been drinking, has invited her violator to her room, or has had previous sexual relations.

Recently, researchers have been looking at who commits acquaintance rape and why. Social scientists suggest there are certain characteristics that can increase risk factors. For example, overt and subtle messages given to men and boys about what it means to be male - dominant, aggressive, uncompromising - can contribute to a mindset which accepts sexual aggression. Hostile attitudes towards women, condoning force in sexual relationships, and the amount of prior sexual experience all seem to correlate to aggressive sexual behavior among males. Early parental neglect and abuse have also been linked to such behavior.

A newly published study of men aged 17 to 21 who commit intimate partner violence found that more than half of the men surveyed had faced challenges earlier in their lives. "Until now we didn't have much information on young men who hurt their partners," said Dr Elizabeth Miller, Assistant Professor of Pediatrics at the University of California/Davis and a senior author of the report. "This is a critically important piece of the puzzle in terms of designing meaningful prevention and intervention programmes to prevent adolescent relationship violence." The study, published in September in the American Journal of Men's Health, concluded that further research is needed that considers environmental aspects of sexual violence. "We need to look beyond individuals to see how environments [such as family life, school, and peer environments] might promote such behaviors among boys," Dr Reed, the study's lead author, said.

The consequences of date rape can be severe. High levels of anxiety and depression are reported as well as complications in subsequent relationships and difficulty in attaining pre-rape levels of sexual satisfaction. Some women become increasingly withdrawn while others act out sexually, becoming promiscuous as their self-worth diminishes. Post traumatic stress disorder, or PTSD, often occurs.

Preventing acquaintance rape is key to ending it. Experts advise girls and women to realize that date rape exists and is dangerous. They counsel women to be assertive in setting relationship boundaries and in discouraging unwanted physical contact. "Be assertive, not victimized," says one counsellor. "Remember, you can't predict who might be a rapist, so use an individual's behavior as an indicator of intentions. Don't put yourself in awkward situations like drinking too much or being alone with someone on a first date. Make sure that potential offenders know that acquaintance rape is a serious crime that can be prosecuted to the fullest extent of the law. Finally, be prepared to act defensively if feeling threatened. Individual safety and well being are legitimate goals."