The biological and physical evidence collected from a victim of a sexual assault is collectively known as a “rape kit.” The term is also used to describe a case which holds necessary equipment for carrying out an examination on a rape victim. A rape victim is always allowed to decline a rape kit and still receive medical treatment, although collection of evidence is strongly encouraged. In addition to leading police to the perpetrator, a rape kit can also bolster the case in court, should it come to trial.

Being sexually assaulted can be extremely traumatic. For this reason, many communities have Sexual Assault Response Teams (SARTs). The members of a SART receive special training in dealing with victims of assault and collecting evidence. They commonly include medical personnel, law enforcement, and employees of a crisis center who can provide advice, counseling, and support to victims. Generally, SART representatives recommend that a rape kit be collected with 72 hours of a sexual assault.

An examination after a sexual assault usually starts with taking photographs of the victim and collecting his or her clothing. Next, medical personnel treat any emergent injuries which require care, while documenting these injuries for the record. Blood and urine samples are taken, and swabs of the oral and genital area are collected as well. Commonly, samples of the victim's hair will be taken, and a nurse will collect biological evidence which may convict the attacker, such as bodily fluids and hair. In addition, the patient will usually be offered prophylactic treatment for sexually transmitted diseases and pregnancy, if these are concerns.

Since this examination can be upsetting, having all the necessary equipment ready to hand is very important. This minimizes traffic to and from the examination room, allowing the medical staff member to focus on the patient's medical as well as physical care. In many hospitals, there is a special room set aside for the collection of evidence in assault cases. The room may be decorated in a more friendly way, and it often includes a private bathroom.

In many regions, a hospital can collect a rape kit and hold it while the victim decides whether or not to report the crime to the police. Privacy laws may also prevent the hospital from disclosing the name of the victim, although the hospital may report the crime to law enforcement. For patients who are not sure about whether or not they want to prosecute, collecting and storing the rape kit is like a form of insurance.

Once reported to law enforcement, representatives of a criminal lab pick up the rape kit and subject the contents to analysis. Lab work may establish who committed the crime, or at least provide valuable clues. Along with other evidence in criminal cases, a rape kit is closely guarded once it has been collected, to reduce the risk of evidence tampering or contamination.