The study determined that three approaches for accessing the NDNH database could assist in locating convicted sex offenders: individual case inquiries, computerized database matching, and a hybrid approach that would allow States to generate lists of offenders for computerized database matching. This report suggests that the U.S. Congress consider granting the authority to the U.S. Department of Health and Human Services (HHS) administrator of the NDNH, to share information in the NDNH with the FBI for the purposes of locating convicted sex offenders who are being actively sought by law enforcement officials but whose addresses in the National Sex Offender Registry (NSOR) are incorrect, out-of-date, or missing. The report further suggests that Congress consider directing HHS and the FBI to conduct a test match of the information in the NDNH and NSOR to determine the costs and benefits of matching information in the two databases, including an assessment of the validity of the matches. This study reviewed relevant laws, memoranda of understanding, and agency guidance to identify legal and other barriers that might prevent law enforcement officials from receiving NDNH information. This information was also used to identify approaches for using NDNH information to update sex offender registries. Researchers also analyzed the contents of the NSOR and NDNH to determine whether the systems shared unique identifiers that permitted matching information in the two databases. The reliability of NDNH and NSOR data was assessed through interviews with key officials from HHS and the FBI.