The AA. studied ninety children affected by microscopic hematuria whose origin was not clear. Periodic controls have been effectuated during a period from one to five years. The hematuria is spontaneously disappeared in the 46,7% of the cases. In sixteen children (17,7%) the hematuria was also present in some relatives, nine children were affected by urinary tract malformations. Only twenty subjects were affected by a significant renal pathology.