To establish the role of electron microscopy in the diagnosis of glomerular diseases we reviewed retrospectively 113 renal biopsies. The biopsies were included in this study if tissue was received for light microscopy, immunofluorescence and electron microscopy. The biopsy was assigned to one of the three following categories on the contribution of the ultrastructural findings to the primary diagnosis: essential, important, and not required. Our study revealed that electron microscopy was essential to establish the primary diagnosis in 35 cases (31.0%), was important, but did not alter the preliminary diagnosis in 15 cases (13.3%) and in 63 cases (55.7%) the ultrastructural examination was not needed to confirm the diagnosis. Electron microscopy was essential to create diagnosis in a total of two cases of thin basement membrane disease, in nephropathy in Alport syndrome, in nephropathy in Fabry disease, and was necessary for establishing final diagnosis in 12 cases (85.7%) of minimal lesion. On the basis of electron microscopy it was also possible to establish the precise diagnosis of subtypes in mesangiocapillary glomerulonephritides, describe the stage of membranous glomerulopathy, and find thickening of glomerular basement membrane in the pre-diabetic state. Moreover, ultrastructural examination was helpful to differentiate membranous and mesangiocapillary glomerulonephritis, minimal change nephropathy and early membranous lesions, and distinguish membranous lupus nephritis from idiopathic membranous nephropathy The electron microscopy findings were not of any help in establishing the diagnosis and did not obtain any valuable information in all cases of amyloid nephropathy and IgA nephropathy, as well as in the majority of focal segmental glomerulosclerosis, extracapillary glomerulonephritides, and mesangial proliferative glomerulopathies. In conclusion, the results showed that in 44.3% of glomerulopathies the ultrastructural study provides fundamental or important diagnostic information, and therefore electron microscopy still remains a useful tool in the diagnosis of glomerular diseases.