The aim of this study is to assess mortality risk and the excess of risk in patients with diabetes. Patients were 15-34 years old at diagnosis of diabetes mellitus (n = 879) in 1992 and 1993 in this national cohort from Sweden. Healthy controls were matched for gender and birth on the same day as the index cases (n = 837). The civic registration number was used to link patients and controls to the Swedish Cause of Death Registry. During follow-up, 3.3% (29/879) of patients and 1.1% (9/837; P = 0.002) of controls died. The risk for a patient with diabetes to die was almost threefold increased compared with healthy controls; hazard ratio, 2.9 (95% CI 1.4-6.2). This increased risk was significant in men; hazard ratio, 2.8 (95% CI 1.2-6.5). Diabetes as the underlying cause of death accounted for 38% (11/29) of deaths among patients. Most patients, 55% (16/29), died at home, remaining patients in hospital, 28% (8/29), or elsewhere 17% (5/29) compared to controls of whom 33% (3/9; P = 0.45) died at home, 33% (3/9; P = 1.0) in hospital, and 33% (3/9; P = 0.36) elsewhere. Only 55% (16/29) of patients had a specified day of death on death certificates compared to 100% (9/9; P = 0.016) of controls. Adult men with diabetes had an almost threefold increased risk to die within 15 years of diagnosis compared to healthy men. Most middle-aged patients with diabetes died at home and often without a specified date of death recorded.