Analysis of the official Swiss mortality data have shown considerable social differences. In an earlier study of Swiss men aged 15-74 for the period 1979-1982 the social class mortality differentials have been analysed using standardized mortality ratios (SMR). The present study extends this previous work by calculating years of potential life lost (YPLL) before age 75, an additional indicator of mortality that puts more importance on deaths at younger ages. Emphasis is given on causes contributing to most years of life lost, especially to accidents and violent deaths, which result in more than 30% of total years of life lost. The distribution of years of life lost of the most important causes to social classes is illustrated also for age-specific groups. Additionally, this article presents all causes which account for more than 3% of total years of life lost. The social inequalities are shown as ratios between the social class with the highest (skilled manual workers) and the lowest risk (professionals). Most years of life are lost by skilled manual workers not only in general but also cause-specific. While the SMR from all causes of death showed a 2-fold difference between professionals and skilled manual workers, the social gradient in YPLL rate was even larger (2.5). Hence, the measure of years of potential life lost emphasizes the disadvantage of skilled manual workers to die earlier than professionals. The concept of YPLL proved to be a useful additional indicator not only of mortality in general, but also especially for monitoring causes, related to the lower social classes.