BACKGROUND: Little information is available on temporal trend in socioeconomic inequalities in cause of death mortality in France. The aim of this paper was to study educational differences in mortality in France by cause of death and their temporal trend. METHODS: We used a representative sample of 1% of the French population and compared four periods (1968-1974, 1975-1981, 1982-1988, 1990-1996). Causes of death were obtained by direct linkage with the French national death registry. Education was measured at the beginning of each period, and educational disparities in mortality were studied among men and women aged 30-64 at the beginning of each period. Analyses were conducted for all deaths and for the following causes of death: all cancers, lung cancer (among men), upper aerodigestive tract cancers (among men), breast cancer (among women), colorectal cancer, other cancers, cardiovascular diseases, ischaemic heart diseases, cerebrovascular diseases, other cardiovascular diseases, external causes, other causes of death. Socioeconomic inequalities were quantified with relative risks and relative indices of inequality. The relative indices of inequality measures socioeconomic inequalities across the population and can be interpreted as the ratio of mortality rates of those with the lowest to those with the highest socioeconomic status. RESULTS: Analyses showed an increase in educational differences in all cause mortality among men (the relative indices of inequality increased from 1.96 to 2.77 from the first to the last period) and among women (the relative indices of inequality increased from 1.87 to 2.53). Socioeconomic inequalities increased for all cause of death studied among women, and for cancer and cardiovascular diseases among men. The contribution of cancer mortality to difference in overall mortality between the lowest and the highest levels of education increased strongly over the whole study period, especially among women. CONCLUSION: This study shows that large socioeconomic inequalities in mortality are observed in France, and that they increase over time among men and women.