Since 1998, by law, all school children in Korea must have an annual urinalysis. The first early morning urine specimen is examined by a simple dipstick method for the detection of proteinuria, haematuria and glucose. If a urine test is positive, a second test is performed by paediatric nephrologists. We analysed urinalysis data of school urinalysis screening. We also analysed the results of clinical data and the renal biopsy findings of patients referred to our medical centre due to abnormal urinalysis result. To date, about five million students have been screened since annual school urinalysis started in January 1998. Among them, isolated proteinuria was about 0.2%, occult blood was about 0.8%, and glucosuria was about 0.07% from January 1998 to December 2004. Among referred patients, renal biopsy was taken in 63.1% of isolated haematuria, 10.5% of isolated proteinuria and 69.9% of haematuria combined with proteinuria. Histopathological findings are IgA nephropathy in 43.8%, mesangial proliferative glomerulonephritis in 38.4%, Henoch-Schönlein nephritis in 2.7%, membranoproliferative glomerulonephritis in 1.6% and lupus nephritis in 0.5%. Alport disease showed 0.6% as a hereditary disease. In conclusion, the school urinalysis screening could detect chronic renal disease in its early stage. Early detection using school urinalysis screening and confirmatory diagnosis by renal biopsy seems to be helpful for assessment of prognosis and intervention of chronic renal disease progression.