OBJECTIVE: Diabetic nephropathy is one of the most serious complications of diabetes mellitus. It develops in approximately one-third of diabetic patients, years after the onset of metabolic abnormalities. STUDY DESIGN: The biopsy specimens were evaluated with the focus on light microscopy. The aim of our study was to reveal differences in the details and the frequency of occurrence of individual histomorphological changes in diabetic nephropathy and other glomerulonephritides. RESULTS: Diabetic nephropathy accounted for 14 out of 82 analyzed biopsies. Isolated thickening of the glomerular basement membrane was not present in any case, but along with some degree of mesangial expansion, hypercellularity or glomerulosclerosis was seen in 12 out of 14 findings of diabetic nephropathy. In other glomerular diseases, mesangial changes, but without glomerular basement membrane thickening, were the most frequent findings. In addition to glomerular lesions, some of the tubular, interstitial, and vascular changes were seen in 13 out of 14 patients with diabetic nephropathy. In other glomerulonephritides the combination of all these changes was a rare finding. CONCLUSION: There are cases where immunofluorescence and electron microscopy cannot be performed or their results are not helpful. In such cases we must rely on light microscopic histomorphological changes. © Science Printers and Publishers, Inc.