Between the years 1979 and 2004, an average of 413 unidentified persons died each year. The peak year was 1987, with 691 unidentified decedents, a rate of 28.4 per 10 million people. The rate declined to 9.7 per 10 million in 2004. Most of the unidentified decedents were male (80.6 percent). The rates of unidentified decedents were highest among Blacks, and the greatest percentage lived in the Southwest. Among deaths for which the cause was known, 82.7 percent were due to injuries. Among injury deaths, 31.8 percent were homicide. Improvement in technology relevant to identifying decedents may have reduced rates of John and Jane Does since the 1980s. In addition, variations in rates of unidentified decedents may reflect changes in risk factors, such as homelessness and substance abuse. This was a population-based surveillance study of data collected from death certificates from 1979 to 2004 in the United States. The Centers for Disease Control and Prevention’s National Center for Health Statistics (NCHS) receives death certificate information from the vital registrars in all State and U.S. Territories. In order to create a database of unidentified decedents, NCHS searched more than 50 million death certificate records in the National Death Index file for the designated years. An unidentified person was defined as a person whose name, date of birth, and Social Security number was missing from the death certificate. 3 tables, 3 figures, and 27 references