Background: Cardiovascular risk is higher among people with diabetic nephropathy than among those with normal renal function. Carotid intima-media thickness (IMT) is an independent predictor of cardiovascular mortality in type 2 diabetic patients. However, the relationship between carotid IMT and diabetic nephropathy is not well known. The aim of our study was to elucidate whether carotid IMT is associated with progression of diabetic nephropathy in type 2 diabetic patients. Methods: We recruited a total of 354 type 2 diabetic patients with diabetic nephropathy. Renal function was evaluated by serum creatinine levels, estimated glomerular filtration rate (eGFR), and urinary albumin/creatinine ratio (ACR). Carotid IMT was assessed using B-mode ultrasound by measuring generally used parameters. Baseline-to-study end changes in eGFR were calculated, and the yearly change of eGFR (mL/min/yr) was computed. Results: Age, diabetes duration, ACR, and eGFR were significantly correlated with mean or maximal carotid IMT; however, lipid profiles, HbA1c, and blood pressure were not correlated. The mean yearly eGFR change was -4.9 ± 5.3 mL/min/yr. The yearly eGFR change was negatively correlated with mean and maximal carotid IMT. After adjusting for age and diabetes duration, the mean IMT is an independent predictor of yearly eGFR change. Conclusion: Carotid IMT may be a predictor of diabetic nephropathy progression in patients with type 2 diabetes. (Endocrinol Metab 26:310-316, 2011)