Objective To differentiate proteinuria due to non-diabetic renal diseases(NDRD)from that of diabetic nephropathy(DN)in type 2 diabetic patients,and to evaluate the prevalence of NDRD.Methods A retrospective analysis was performed on diabetic patients who had undergone renal biopsy between Jan 1,2003 and Dec 3 1,2006.The data including history of diabetes,cardiac color ultrasound,color Doppler ultrasound of the carotid artery,retinal changes,examination of ocular fundus,giomerular filtration rate,hepatic and renal function,lipid profile,blood glucose,HbA1c,and urine protein were collected.Results Among 46 patients,22 cases (47.8%)were distinctly diagnosed as diabetic nephropathy(DN),while the other 24(52.2%)as NDRD.Focal segmental glomeruloselerosis Was the most common lesion found in patients with NDRD.In DN group,the fasting blood glucose was higher than that of NDRD group,as well as ejection fraction,carotid plaque,and intimamedia thickness(IMT)showed significant differences between 2 groups.Patients with NDRD were less frequently associated with diabetic retinopathy.Diabetic retinopathy showed hiigh sensitivity(72.7%)and specificity (91.7%)in diagnosing DN.Conclusions Blood glucose,ejection fraction,carotid plaques and IMT,and retinopathy may be helpful in differential diagnosis of diabetic patients with overt proteinuria.Renal biopsy is an important step lo establish the diagnosis.