Very little is known about the role of medical evidence in the legal resolution of sexual assault cases. A retrospective review of hospital and police records was conducted to determine whether medico-legal evidence was related to the police laying of charges. Data were obtained from 187 female sexual assault victims who presented to a large urban hospital-based sexual assault treatment center and the police in Ontario, Canada between January 1 and December 31, 1994. Using stepwise logistic regression medico-legal variables were tested while controlling for non-medical factors. Neither the collection of sperm, semen and/or saliva nor the documentation of clinically observed injuries was significant in predicting an arrest and charge. In contrast, non-medical variables such as the victim's age, use of alcohol, resistance and relationship to the assailant, and the corroborating evidence of a witness were related to charge-laying. We question the value of uncritically continuing to collect medical forensic evidence.