The aim of the present study was to identify the contribution from specific causes of death to the changes in life expectancy at birth in Denmark relative to Sweden in different age groups during the 1980s and to compare the difference in life expectancy between the two countries in 1990. Mortality data from WHO mortality tapes grouped in smaller series of clinically meaningful categories were used to calculate the contribution of each of these categories at each ten year age group to the difference in life expectancy at birth in each country between 1979 and 1990 and between the two countries. During the period from 1979 to 1990 life expectancy increased in both Denmark and Sweden. However, Sweden experienced the greatest increase in life expectancy (more than two years) while it increased less than one year in Denmark. In both countries a decrease in cardiovascular disease mortality contributed most to the increase in life expectancy among males as well as females. Both among males and females the less favourable development in Denmark was mainly caused by differences in mortality trends related to cardio-vascular diseases, respiratory and non-respiratory cancer. Over a short period of time two Nordic countries experienced remarkable, but different changes in mortality. These findings suggest that mortality rates are sensitive to even minor differences in social and cultural factors across countries and over short time periods.