The aim of the present study was to determine whether red or white wine affects urinary protein, 8-hydroxydeoxyguanosine (8-OHdG), and liver-type fatty acid-binding protein (L-FABP) excretion in type 2 diabetic nephropathy patients. Twenty-four type 2 diabetes mellitus patients with nephropathy were randomly allocated to drink a 118-mL (4-oz) glass of red wine (n = 12, group A) or white wine (n = 12, group B) daily for 6 months. Twelve type 2 diabetes mellitus patients with nephropathy who did not drink any wines served as control subjects (group C). Serum creatinine, 24-hour creatinine clearance, hemoglobin A(1c), urinary protein, urinary 8-OHdG, and urinary L-FABP were measured before and 3 and 6 months after the start of the study. In groups A, B, and C, serum creatinine, 24-hour creatinine clearance, and hemoglobin A(1c) changed little during the experimental period. However, urinary protein, 8-OHdG, and L-FABP excretions were significantly decreased at 3 (P < .05) and 6 months (P < .01) compared with the baseline values in group A. In contrast, these markers changed little during the experimental period in groups B and C. Thus, these urinary markers were significantly lower in group A than in groups B and C at 3 and 6 months. These results suggest that red wine is renoprotective whereas white wine has no such effect in type 2 diabetes mellitus patients with nephropathy. The renoprotective effect of red wine may be due in part to its ability to reduce oxidative stress.