As a result, valuable physical evidence may be overlooked or inadvertently allowed to deteriorate biologically. In addition, prosecutors with insufficient academic background must supervise the overall police investigation and orchestrate the presentation of complex biological laboratory results through expert witnesses in order to achieve success in court. By being fully aware of investigatory procedures and the evidence that should be collected, police officers can ensure that a sexual assault case is as complete as possible. Each sexual assault occurs under circumstances unique to the victim, the crime scene, and the suspect. Probative value and relevance to the investigation are watchwords in collecting and preserving evidence. If collected materials are stored in plastic bags at room temperature for any length of time, the biodegrading action of contaminant bacteria may jeopardize conclusive test results. Sexual assault evidence kits are commercially available and stocked by hospitals and rape crisis centers. The prosecutor can be the driving force in organizing local sexual assault investigation training seminars for police officers, health professionals, and crime laboratory personnel. Additional information on the role of serology and DNA profiling in sexual assault cases is appended. 5 references