Post-communist transition has had a huge impact on mortality in Eastern Europe. We examined how educational inequalities in mortality changed between 1990 and 2000 in Estonia, Lithuania, Poland and Hungary. Cross-sectional data for the years around 1990 and 2000 were used. Age-standardized mortality rates and mortality rate ratios (for total mortality only) were calculated for men and women aged 35-64 in three educational categories, for five broad cause-of-death groups and for five (seven among women) specific causes of death. Educational inequalities in mortality increased in all four countries but in two completely different ways. In Poland and Hungary, mortality rates decreased or remained the same in all educational groups. In Estonia and Lithuania, mortality rates decreased among the highly educated, but increased among those of low education. In Estonia and Lithuania, for men and women combined, external causes and circulatory diseases contributed most to the increasing educational gap in total mortality. Different trends were observed between the two former Soviet republics and the two Central Eastern European countries. This divergence can be related to differences in socioeconomic development during the 1990s and in particular, to the spread of poverty, deprivation and marginalization. Alcohol and psychosocial stress may also have been important mediating factors.