AIM: To estimate the risk of diabetic nephropathy and associated risk factors in a nationwide cohort of childhood-onset type 1 diabetes mellitus (T1DM) and 19-30 yr of diabetes duration. METHODS: Patients diagnosed with childhood-onset T1DM ( 200 microg/min, respectively] in at least two out of three consecutive overnight urine samples were defined as diabetic nephropathy. RESULTS: Overt nephropathy was found in 7.8% [95% confidence interval (CI) 4.7-10.9] and persistent microalbuminuria in 14.9% (95% CI 10.8-19.0) of the subjects. Hemoglobin A1c (HbA1c) (p = 0.001), systolic blood pressure (BP) (p = 0.002), total cholesterol (p = 0.019), and C-reactive protein (CRP) (p = 0.019) were associated with diabetic nephropathy. Significant predictors in 1989-1990 for the development of diabetic nephropathy in 2002-2003 were HbA1c (p