The significance of the presence of podocytes in the urine was studied in various renal diseases in children. The podocytes were detected by immunofluorescence using monoclonal antibodies against the podocalyxin that is present on the surface of podocytes which serves as a glycocalyx. They were scored according to the numbers per partitioned area on cytospun urine sediments. Urine podocytes were absent in normal control, nonglomerular diseases such as urinary tract infection and nonglomerular hematuria, and glomerular, noninflammatory diseases such as minimal change nephrotic syndrome and membranous nephropathy. Conversely, the excretion of podocytes in the urine were detected in various glomerular, inflammatory diseases. A significantly higher level of the podocyte score was found in the acute state of glomerular diseases which was defined as within 6 months after disease onset. Positive correlations were obtained between the presence of urinary podocytes and the histological features of active extracapillary changes and mesangial proliferation. Urinary podocytes were examined monthly for 12 months in 7 cases with IgA nephropathy and 2 cases with Henoch-Schönlein purpura nephritis, and a consistently higher urinary podocyte score was observed in the patients with histological progression. The scoring of urinary podocytes was found to be useful clinically, as a diagnostic tool for glomerular or nonglomerular diseases, inflammatory or noninflammatory diseases, a marker for the estimation of the severity of active glomerular injury and also as a predictor of disease progression.