BACKGROUND Medical legal investigations in the United States (primarily unnatural or suspected unnatural deaths) are carried out by medical examiner or coroner systems. Medical examiners-usually physicians and generally with training in pathology, medicolegal death investigation, and performance of forensic autopsies-generally have greater expertise in unnatural death investigations than do coroners. OBJECTIVE To document the locations and implementation year for states and counties that have medical examiner systems that have replaced coroner systems or that are defined in statute and assist coroners in their investigations. METHODS Review of published information and national survey in 1997. METHODS United States. METHODS County medical examiners and state medical examiners or their administrators. METHODS The location of states and counties with medical examiner systems, the implementation year for each system, and the proportion of counties and population served by medical examiner systems. RESULTS A total of 79 of 91 county medical examiners responded. A total of 36 states have at least 1 medical examiner system at the county, district, or state level in which there is no coroner involved in the death investigation process. Only 22 states have medical examiner death investigation systems in place and have no coroners in the state. Among 13 states in which some counties have coroner systems and some have medical examiner systems, medical examiner systems exist in 8% of counties and serve 43% of the population. Medical examiner systems that operate without coroner involvement serve about 48% of the population nationwide. Few state or county medical examiner systems have been implemented since 1990. CONCLUSIONS In this century, medical examiner systems have gradually replaced coroner systems, but such change has slowed in recent years, with medical examiner systems now serving about 48% of the national population.