BACKGROUND. Mortality from vascular diseases has been reported to be high in diabetic persons. METHODS. To evaluate mortality from these and other specific causes, we examined cause-specific age-sex standardized mortality ratios in a geographically defined population of younger onset (diagnosed before age 30 and taking insulin, n = 1200) and older onset (diagnosed after age 30, n = 1772) diabetic persons followed for 8.5 years. Cause of death was determined from death certificates. RESULTS. In younger onset persons, age-sex standardized mortality ratios were significantly high (P less than .05) for all causes of death (7.5) as well as for diabetes (191), all heart disease (9.1), ischemic heart disease (10.1), other heart disease (6.3), nephritis and nephrosis (41.2), accidents (2.9), and all other causes (3.2). In older onset persons, age-sex standardized mortality ratios were significantly high for all causes of death (2.0) as well as for diabetes (16.8), all heart disease (2.3), ischemic heart disease (2.3), other heart disease (2.1), stroke (2.0), and pneumonia and influenza (1.7). CONCLUSIONS. Diabetic persons experience very high mortality, especially from vascular diseases, compared to the general population.