Thin basement membrane disease is more common than IgA nephropathy or Alport syndrome, which are also associated with the presence of erythrocyturia. Very few reports on the disorder are available in the Polish literature. The objective of this work was to analyze the results from 83 patients with thin basement membrane syndrome as well as to formulate a proposal of strict morphological assessment criteria for the disorder. Attention was drawn to the requirement of thickness of the lamina densa rather than the entire basement membrane thickness and a sufficiently high number of loops featuring thinned lamina densa, namely at least 80% of loops, being taken into account. Occurrence of other morphological changes associated with the disorder and clinical symptoms other than erythrocyturia was also highlighted.