By the judgement of erythrocyte morphology in urinary sediment it is possible to recognize the origin of hematuria. In glomerular hematuria the cells show destructive changes so that a differentiation is possible contrary to the regular formed erythrocytes from bleeding sources of the urinary tract. The urinary sediments of 325 patients (185 cases with glomerulonephritis and 140 cases with urolithiasis) are judged independently by two study groups. In glomerulonephritis 90.5 +/- 7.4% dysmorphic erythrocytes were found, whereas in urolithiasis the portion of destructed cells was 5.7 +/- 5.4%. In 95% of the patients the origin of hematuria could be verified by microscopical erythrocyte analysis.