There is a sharp divide in mortality between eastern and western Europe, which has largely developed over the past three decades and is caused mainly by chronic diseases in adulthood. The difference in life expectancy at birth between the best and worst European countries in this respect is more than 10 years for both sexes. The reasons for these differences in mortality are not clear and data currently available permit only speculation. The contributions of medical care and pollution are likely to be modest; health behaviour, diet, and alcohol consumption seem to be more important; smoking seems to have the largest impact. There is also evidence that psychosocial factors are less favourable in eastern Europe. Available data show socioeconomic gradients in all cause mortality within eastern European countries similar to those in the West. Determinants of the mortality gap between eastern and western Europe are probably related to the contrast in their social environments and may be similar to those underlying the social gradients in mortality within countries.