Blood in the urine can be caused by a wide spectrum of conditions in childhood, from simple urinary tract infections to severe, rapidly progressing glomerulonephritis leading to rapid deterioration of kidney function. Therefore, during the investigation of hematuria, our main goal is to identify cases that are medically significant. Proteinuria associated with hematuria, high blood pressure, or reduced kidney function suggests progressive kidney disease. If the hematuria is macroscopic or further clinical symptoms are characteristic, the differential diagnosis is usually easy and clear. How ever, in more complicated cases, additional noninvasive examination methods may be necessary, such as ultrasound, examination of red blood cell morphology, calcium excretion, other chemical parameters of urine, and determination of kidney function and the degree of proteinuria. A detailed family history helps identify hereditary causes of hematu ria. In the case of asymptomatic hematuria, the indication for performing a kidney biopsy may vary depending on the local clinical practice. Furthermore, the diagnosis rate of glomerular diseases is significantly influenced by the criteria for performing a kidney biopsy. In our review, we present the challenges of diagnosing hematuria as the definition, the steps to differentiate glomerular and postglomerular causes, and review the most common underlying diseases, which present a challenge in our daily clinical practice due to their high frequency or rapid course and poor prognosis.