BACKGROUND: The purpose of the study was to determine trends in social inequality in mortality and life expectancy in Denmark. METHODS: The study was based on register data on educational level and mortality during the period 1981-2005 and comprised all deaths among Danes aged 30-60. Sex- and age-specific death rates for each of three levels of education were calculated and age-standardized to allow comparisons over time and between groups. As data obtained since 1996 included ages up to 74, partial life expectancy (i.e. expected lifetime of 30-year-olds before the age of 75) was calculated for the period 1996-2005. RESULTS: Between 1981 and 2005, the difference in death rates between people aged 30-60 with low and high educational level increased by two-thirds for men and was doubled for women. During the period 1996-2005, the gap in partial life expectancy from age 30 to 75 between people with low and high educational level increased by 0.3 years. CONCLUSION: During the past 25 years, the social gap in mortality has widened in Denmark. In particular, women with a low educational level have been left behind.