Purpose : This study was performed to report the diagnosis and treatment of nephrotic syndrome manifesting in the first year of life. Methods : We retrospectively reviewed the clinical data with chart review in 7 patients who were diagnosed as nephrotic syndrome manifesting in the first year of life from 1996 to 2007. Results : Three patients had congenital nephrotic syndrome, the other 4 patients had infantile nephrotic syndrome. Their ages ranged from birth to 11 months and male to female ratio was 1 to 6. Renal biopsies were done in 6 patients. One patient had Finnish type congenital nephrotic syndrome, 2 patients had diffuse mesangial sclerosis, 2 patients had focal segmental glomerulosclerosis and 1 patient had minimal change disease. Genetic analyses of NPHS2, PLCE1, and WT1 were done in 4 patients and 2 of them had WT1 mutation. Among 3 patients with congenital nephrotic syndrome, 1 patient was diagnosed as congenital nephrotic syndrome of Finnish type and the other 2 patients were diagnosed as Denys-Drash syndrome. All of the patients with congenital nephrotic syndrome died due to sepsis. Among 4 patients with infantile nephrotic syndrome, 2 patients died and 1 had remission, another patient progressed to end stage renal disease. Conclusion : Most of nephrotic syndrome manifesting in the first year was hereditary renal disease. Patients with nephrotic syndrome manifesting in the 3 month of life had poorer prognosis and needed more aggressive management including early dialysis and renal transplantation might be considered compared with infantile nephrotic syndrome. Further genotype-phenotype correlation studies are needed.