OBJECTIVES: To estimate the impact of diseases on social differences in life expectancy and expected lifetime with illness among Danes in 1995-99. METHODS: Expected lifetime with and without long-standing illness were calculated for groups with low, medium and high educational levels. Estimates based on observed rates of mortality and prevalence of illness were compared with those based on rates from which a specific disease had been eliminated. RESULTS: Partial life expectancy (age 30-75) would increase by almost 1.5 years if cancer were eliminated. Expected lifetime without long-standing illness would increase by approximately 1 year. Elimination of cardiovascular diseases would increase partial life expectancy, mainly among men with a low educational level. If diseases of the musculoskeletal system were eliminated the benefit would be greatest for persons with a low educational level. CONCLUSIONS: The gain in life expectancy to be expected by eliminating certain diseases decreased with educational level. Elimination of cancer would extend lifetime both with and without illness for all educational levels.