IgA nephropathy (IgAN), which is a major cause of glomerulonephritis (GN), reaches to end-stage renal disease (ESRD) among 10~50% of patients over 20 years. Since IgAN had a diverse range of clinical presentation from simple microscopic hematuria to rapid progression, predicting renal outcome would be helpful to approach treatment strategy. We evaluated renal outcome as applying a new chronicity scoring system of IgAN, which is consisted of 4 factors including glomerulosclerosis, tubular atrophy, interstitial fibrosis and arteriosclerosis A total of 7104 IgAN patients diagnosed to IgAN by kidney biopsy from January 1st, 1979 to October 10th, 2018 were enrolled from Korean GlomeruloNephritis Study Group (KOGNET) registry. The patients were divided into four groups based on grade of chronic scoring system analysis (minimal: 0-1, mild: 2-4, moderate: 5-7, severe: 8-10). Primary outcome was a period for doubling of serum creatinine level, Secondary outcome was renal survival through a progression to ESRD. Renal outcome was assessed based on grade of chronicity scoring via Kaplan-Meier. For doubling of serum creatinine level, the minimal and the mild groups showed greater renal outcomes than the moderate and the severe groups (P<0.001 for all and P<0.001 for all, respectively). However, there were no significant difference of renal outcome between moderate group and severe group (P=0.51). The renal survival from ESRD represented that the minimal group had greatest renal survival than mild, moderate and severe group (P<0.001 for all), and mild group had better renal survival than moderate and severe group (P<001, P<001, respectively). In the IgAN patients with lower score based on chronicity scoring system showed slow progression to ESRD compared to those with advanced chronicity.