The investigation of allegations of sexual assault requires appropriate medical examinations and forensic sampling of both complainant and the alleged perpetrator. Such examinations require knowledge of normal human anatomy and physiology, principles of appropriate examination, appropriate methods of assessment and forensic sampling, appropriate means of documentation, and a full awareness of the possible clinical findings following sexual assault. The interpretation of findings will also require an awareness of law in the relevant jurisdiction. This chapter addresses these issues from the perspective of the England & Wales jurisdiction, but the broad medical principles of history taking, clinical examination and forensic sampling are applicable worldwide.