PURPOSE: Idiopathic nephrotic syndrome (NS) can be clinically classified as steroid-sensitive and steroid-resistant. The detailed mechanism of glucocorticoid action in NS is currently unknown. METHODS: In this study, we investigated 3 known single nucleotide polymorphisms (SNPs) (ER22/23EK, N363S, and BclI) of the glucocorticoid receptor gene (the NR3C1 gene) in 190 children with NS using polymerase chain reaction-restriction fragment length polymorphism and analyzed the correlation between the genotypes and clinicopathologic features of the patients. RESULTS: Eighty patients (42.1%) were initial steroid nonresponders, of which 31 (16.3% of the total) developed end-stage renal disease during follow-up. Renal biopsy findings of 133 patients were available, of which 36 (31.9%) showed minimal changes in NS and 77 (68.1%) had focal segmental glomerulosclerosis. The distribution of the BclI genotypes was comparable between the patient and control groups, and the G allele frequencies in both the groups were almost the same. The ER22/23EK and N363S genotypes were homogenous as ER/ER and NN, respectively, in all the patients and in 100 control subjects. The BclI genotype showed no correlation with the NS onset age, initial steroid responsiveness, renal pathologic findings, or progression to end-stage renal disease. CONCLUSION: These data suggested that the ER22/23EK, N363S, and BclI SNPs in the NR3C1 gene do not affect the development of NS, initial steroid responsiveness, renal pathologic lesion, and progression to end-stage renal disease in Korean children with NS.