To find out the prevalence of suicides and other types of self-destructive behaviour in fatal motor traffic accidents in Finland, all the data on fatal accidents compiled by road accident investigation teams in the years 1987-1988 and 1991-1992 were investigated. The results were compared to an earlier study covering the years 1974-1975 and 1984-1985. The two 4-year periods covered a total of 2440 cases, which were classified into four groups: suicides, unclears, negligents and 'true' accidents. During the studied, nearly 20-year period, the number of suicides and negligent drivers had increased significantly. Also the relative proportion of suicides had increased from 1.1% to 7.4% and the relative proportion of negligents from 11.2% to 20.0%. There were no significant changes in the number of unclear cases. Suicide and unclear cases were similar to each other in many respects, whereas the negligent cases differed from these two. Most of the drivers were males in each of the three groups. Single-vehicle accidents were typical in the negligent group and collisions in the other groups. The drivers in the negligent group were younger than the drivers in the suicide and unclear groups. At the time of the accident, the most common mental state among suicide drivers was 'depression'.