The epidemiologic necropsy for abdominal aortic aneurysm. The epidemiologic necropsy measures the occurrence of unsuspected disease through the examination of necropsy records. The estimates of unsuspected disease should approximate what occurs in the living population. The necropsy records of the University of Kansas Medical Center (Kansas City) from 1950 to 1984 were examined for the occurrence rate of abdominal aortic aneurysms. Each adult patient was categorized as (1) without abdominal aortic aneurysm, (2) abdominal aortic aneurysm discovered as a necropsy surprise, or (3) abdominal aortic aneurysm diagnosed or suspected during life. Necropsy detection rates of unsuspected abdominal aortic aneurysms were compared with those found in five published screening surveys. The necropsy detection rate in men was 81 (0.019) of 4155 and was 28 (0.009) of 3142 in women, a difference that was statistically significant. When the necropsy series was adjusted to reflect the same demographic composition as the screening surveys, the results from necropsy and screening were statistically similar. In particular, two surveys from the United Kingdom showed screening detection rates among white men of 0.072 compared with a necropsy detection rate of 0.058. These results further support the use of the epidemiologic necropsy as a research tool for estimating the reservoir of disease in the population. 