Background: IgA nephropathy (IgAN) is the most common primary glomerulonephritis in Korea. To investigate the risk factors for progression, we retrospectively analyzed the data of IgAN from a single center in Korea. METHODS: Three hundred and twenty nine patients (M: F 173:156, mean age 33.96) with biopsy-proven IgAN (January 2002 ~ December 2009) were available for analysis. Progression was defined as an occurrance of CKD stage 3 (eGFR<60 mL/min/1.73m2 by MDRD) or start of renal replacement treatment (RRT) due to ESRD. Cox regression analysis was used and presented as Odd ratio (OR; 95% CI). RESULTS: Number of patients with episodic gross hematuria, microscopic hematuria with proteinuria, nephritic syndrome and hypertension as an initial clinical presentation was 42 (12.8%), 203 (61.7%), 5 (1.5%) and 60 (18%), respectively. At presentation, mean creatinine and protein-creatinine ratio (PCR) by spot urine was 0.99±0.98 mg/dl and 970±130 mg/g. Number of patients with glomerulosclerosis in renal biopsy was 151 (45%). During mean follow-up of 43 months (range 12~101), 14 (4.3%) patients had begun RRT and 28 (8.2%) patients were diagnosed as CKD stage 3 and above. With univariant analysis, age at diagnosis (p=0.014, OR=1.049 CI 1.010-1.090), glomerulosclerosis on pathology (p=0.02, OR=7.885 Cl 2.074-29.982) and PCR >500 mg/g (p=0.013, OR=6.668, Cl 1.498-29.672) were associated with occurrence of CKD stage 3. Glomerulosclerosis (p=0.01, OR=1.55 Cl 1.071-2.257) and hypertension (p=0.025, OR=3.55 Cl 0.432-1.126) were associated with start of RRT. With multivariant analysis, age at diagnosis, glomerulosclerosis and PCR 500 mg/g were independent risk factor for occurrance of CKD stage 3 and above. CONCLUSIONS: Our study suggests that age at diagnosis, hypertension, proteinuria more than 500 mg/g and glomerulosclelosis on biopsy are major risk factors for progression to CKD 3 and above in Korean patients with IgA nephropathy.