Background: Not a few studies have investigated the clinical association between obesity and renal dysfunction. Nonetheless, there is still scarcity of information about the degree of obesity with the development of microalbuminuria. Thus, we evaluate the longitudinal relationship between the degree of obesity stratified by body mass index (BMI) and the risk for microalbuminuria. Method: A cohort of 1,938 Korean men with normoalbuminuria in 2005 was followed-up until 2010. The development of microalbuminuria was defined as urine-albumin to creatinine ratio (UACR) between 30 and 300 µg/mg and the incidences of microalbuminuria were compared among 4 groups according to their baseline degree of obesity stratified by BMI. Cox proportional hazard model was used to evaluate the hazard ratios (HRs) for microalbuminuria according to the degree of obesity. Result: During follow-up, 103 cases of microalbuminuria (5.4%) developed. The incidence of microalbuminuria was lowest in normal BMI group (underweight: 3.4%, normal: 2.6%, overweight: 4.2%, obesity: 7.9%, P<0.001). When HRs for microalbuminuria in normal BMI group was set as a reference, only obese group had the statistically significant association with the development of microalbuminuria [underweight: 1.73 (0.22-13.49), overweight: 1.49 (0.73-3.06), obese: 2.54 (1.31-4.93), respectively]. Conclusion: Comparing to normal BMI group, people with obesity had the higher risk for microalbuminuria. This study suggests that obesity is longitudinally related to the development of microalbuminuria.