Purpose : The prognosis of acute poststreptococcal glomerulonephritis(APSGN) has been reported to be favorable. However, several studies have reported that patients with nephrotic range proteinuria in the acute phase or persistent proteinuria may progress to chronic renal failure. To elucidate this further, we analyzed the features of proteinuria and its prognosis in pediatric patients with APSGN. Methods : A total of 48 children with APSGN admitted to our hospital between Jan. 2000 and Dec. 2004 were included. After discharge from the hospital, patients were regularly followed up every month by clinical evaluations and laboratory tests including routine urinalysis and quantification of proteinuria. Results : Age of the patients ranged from 3 to 15 years(median 5.8 years) at the time of disease onset. Proteinuria was present in 34(70.8%) patients and 5 of them showed heavy proteinuria. Proteinuria normalized within one month in most patients(82.3%) and there was no one with proteinuria after 6 months. Cyclosporine A(5 mg/kg/day in two divided doses) was given to 3 patients with massive proteinuria that lasted longer than 2 months and the result was complete remission within 4 months. Conclusions : Our data indicated that the prognosis of APSGN during childhood is excellent. Children with severe proteinuria or subnormal renal function in poststreptococcal glomerulonephritis had favorable prognosis without chronic renal failure, and children with crescentic formation also had favorable prognosis. Three patients who continued to have heavy proteinuria for more than 2 months received cyclosporine A and remission of proteinuria was achieved within a couple of months.