The research covered 7,973 medicolegal autopsies in Helsinki and Turku, Finland from 1986 to 1990. Blood samples were taken from cadavers before autopsy when possible and tested using an enzyme immunoassay technique. The investigation included 47.4 percent and 39.2 percent, respectively, of all deaths under the age of 65 years in the metropolitan areas of Helsinki and Turku. Nine HIV-positive cases were detected among the medicolegal autopsies. This figure was higher than the prevalence of 0.01 to 0.03 percent in voluntary screening programs for the general population. Seven cases had previously tested positive and two were previously unknown cases, indicating that people at high risk are clustered in the medicolegal autopsy series. Of six cases in an early stage of infection, three committed suicide, suggesting the importance of HIV screening in suicide cases to trace symptomless HIV carriers. Five cases were detected in 1990, a year when the number of new HIV infection cases in Finland more than doubled compared to the previous 2 years. The authors conclude that testing medicolegal autopsies provides useful information relevant to the general population, even in low prevalence areas like Finland. Such testing has no ethical problems and may be particularly sensitive to early changes in epidemiology. 16 references and 3 tables