Aims/hypothesis: Type 1 diabetic patients with diabetic nephropathy have increased mortality and morbidity compared with normoalbuminuric patients. Telomere length in proliferative cells is inversely related to the total number of cell divisions, and therefore to biological age. We aimed to evaluate differences in telomere length in patients with type 1 diabetes with or without diabetic nephropathy; we also evaluated the prognostic value of telomere length. Methods: In a prospective follow-up study, 157 type 1 diabetic patients with diabetic nephropathy and a control group of 116 patients with type 1 diabetes and normoalbuminuria were followed for 11.1 years (range 0.2-12.9). Telomere length was measured from DNA samples extracted from white blood cells at baseline. Results: The mean telomere length did not differ between patients with or without diabetic nephropathy, and was similar in men and women, but was inversely correlated with age and systolic blood pressure, p<0.05. When dividing patients into tertiles after telomere length, 36 (37%) patients died in the tertile with the shortest telomere length, 24 (28%) died in the middle tertile, and 15 (17%) of patients in the tertile with the longest telomere length died, log rank test p=0.017. After adjustment for traditional risk factors, telomere length was still predictive of all-cause mortality. Conclusions/interpretation: In patients with type 1 diabetes we found no differences in telomere length between patients with or without diabetic nephropathy. We also found that telomere length was associated with all-cause mortality; however, confirmative studies are needed to verify our findings.