Several single-nucleotide polymorphisms of genes related to oxidative stress have been evaluated because intracellular reactive oxygen species are associated with development of diabetes and its microvascular complications. We performed a case-control study to investigate whether V16A polymorphism of manganese superoxide dismutase (Mn-SOD) gene is related to pathogenesis of diabetes and whether the polymorphism is associated with stages of albuminuria in Korean type 2 diabetic patients. Genotype distributions were studied in 178 nondiabetic subjects and 371 type 2 diabetic patients of 3 groups with a normoalbuminuria group (Normo group, n = 244), a microalbuminuria group (Micro group, n = 86), and an overt albuminuria group (Macro group, n = 41). The albumin/creatinine ratio (ACR) was defined as a urinary albumin/creatinine ratio. V16A genotypes were determined with polymerase chain reaction-restriction fragment length polymorphism method. Between nondiabetic subjects and type 2 diabetic patients, Mn-SOD genotype distribution (VV/VA + AA, 146/32 vs 314/57) and A allele frequency (0.121 vs 0.104) were not different. Patients with nephropathy, Micro and Macro groups, had significantly lower A allele frequency, longer diabetic duration, higher prevalence of hypertension, and greater ACR than those of patients without nephropathy (P < .05). A allele was significantly less frequent with progression of nephropathy (Normo group, 0.119; Micro group, 0.073; Macro group, 0.03; P < .05). In type 2 diabetic patients, A allele carriers had significantly lower prevalence of hypertension and lesser ACR than those of A allele noncarriers (P < .01). In multivariate analysis, hypertension, duration of diabetes, serum total cholesterol level, and A allele of Mn-SOD gene were independently associated with stages of albuminuria. These results suggest that V16A polymorphism of Mn-SOD gene is not related to pathogenesis of diabetes but is associated with stages of albuminuria in Korean type 2 diabetes.