Hyperuricosuria (HU), defined as an increased urinary acid excretion, seems to be responsible for the of kidney stone formation. Hyperuricosuria was identified as a potential etiology of hematuria in children and adult patients too. The aim of the study was to analyze clinical course of hyperuricosuria in 77 children (43 girls and 33 boys) treated in 1995-1999. We analyzed familial history of urolithiasis, reasons of hospital admissions, laboratory findings and treatment. HU has been suspected to cause hematuria in patients. Children with higher urinary acid excretion are in increased risk of stone formation.