Current information relating to the clinical significance of proteinuria in children through adolescence was reviewed. Proteinuria may be transient, orthostatic, or fixed. The data indicate that only fixed proteinuria—that is, proteinuria on multiple urine examinations without pos tural exaggeration—may indicate serious glomerular disease. The patient should be followed with periodic but infrequent examinations, avoiding unnecessary, complicated, and hazardous investigations.