All unexpected deaths in New Mexico from 1977 to 1988 were reviewed. By statute each such death must be reported to the Office of the Medical Examiner (OMI) and according to institutional policy autopsied even when death is presumed to be from natural causes. From this group the 650 index cases that form the basis of this report were obtained. The crude rate of sudden, unexpected death among New Mexico residents 5 to 39 years old during the study period was 6.6/100,000 persons at risk. As documented by autopsy, the underlying cause of death in a majority of these cases (53.4%) was related to cardiovascular disease and alcoholism. Male persons in general are at increased risk for sudden, unexpected death, and American Indian and black male persons are at greater risk than their Anglo and Hispanic counterparts. American Indians account for a disproportionate share of the unexpected deaths resulting from alcoholism, and black male persons are at particular risk for unexpected death resulting from cardiovascular diseases. This report emphasizes the importance of life style and diet in the well-being of persons 5 to 39 years old.