The centralised registration and care of all diabetics in a geographically defined population has provided an epidemiological basis for a longitudinal investigation of the prognosis of this disease. Records of all newly diagnosed diabetics who had been registered in the Erfurt district (population 1.25 million) in 1966 were studied in relation to the time period 1966–1976. Of the known 2,560 diabetics (910 men, 1,650 women; 93.7% >40 years of age), 1,054 had died during the 10-year follow-up period. Cardiovascular causes accounted for the majority of deaths (63%). In almost all age classes proportionally more men than women had died at follow-up; there was a significant difference in the 60–69 year group (men 61.6%, women 46.2%). In comparison with the general population, excess mortality ranged from 2.1 to 1.0, decreasing with age at onset without significant differences between men and women. Excess mortality was present in most age classes and was evident within the first year after diagnosis. Current life-table analysis confirmed the shortened life expectancy of the diabetics. The lower lifeexpectancy of noninsul-independent diabetics may not be due to hyperglycaemia alone but probably also involves a variety of atherogenic risk factors.