Suicide is a common cause of death in many Western countries and it has been predicted to become even more common worldwide. The authors analysed socioeconomic differences and trends in Finnish suicide mortality, and assessed the relevance to public health by calculating socioeconomic differences in years of life expectancy lost attributable to suicide. Census records were used, linked with the death records of men and women aged 25 years and over in 1971-2000 in Finland. Suicide among male and female manual workers was 2.3 and 1.3 times higher respectively than among upper non-manual workers. The differences were largest among those in their thirties. Because of the decline in suicide among upper non-manual workers and a slower decrease or even an increase among other socioeconomic groups, the relative mortality differences increased somewhat during 1970-90, then decreased in the 1990s but remained higher than in the 1970s. In 1991-2000 the suicide-related life expectancy gap between the upper non-manual and manual male workers was 0.6 years, and this difference contributed 10% to the total difference in years of life expectancy lost between these socioeconomic groups. Large and persistent socioeconomic differences were found in suicide mortality and suicide was an important component of the socioeconomic difference in total mortality. Reducing these differences could significantly improve equity in health and reduce the burden of excess mortality.