OBJECTIVE: to investigate the level of immunoexpression and the tissue distribution of the TGF-β1 and the ET-1 in the kidney biopsy specimens of the patients with three the most common primary glomerulonephritides, and to examine the possible relationship between the immunoexpression of the cytokines and the course of glomerulonephritis. SUBJECTS AND METHODS: 91 patients who were diagnosed with the primary form of IgA nephropathy (IGAN), membranous nephropathy (MN) or focal segmental glomerulosclerosis (FSGS) were followed prospectively for one year. Initial clinical, laboratory and pathohistological parameters at the time of the renal biopsy as well as the laboratory parameters at the end of follow up period were compared with level of the TGF-β1 and the ET-1 immunoexpression in biopsy specimens. RESULTS: TGF-β1 renal immunoexpression was not significantly higher in comparation to control group. In IGAN patients, glomerular TGF-β1 expression was negatively correlated with the tubulointerstitial fibrosis and with serum creatinine level after one year, in MN group positively correlated with estimated glomerular filtration rate at the end of the study. Opposite results were found with ET-1 expression, where glomerular expression of ET-1 was significantly higher in all three patient subgroups compared to the control group. In IgAN group significant positive correlation is found between glomerular ET-1 expression level and the serume LDL concentration as well as with the endocapillary proliferation. In MN lower baseline serum albumine level and higher 24h proteinuria were corrleated with a higher glomerular ET-1 expression. In FSGS group glomerular ET-1 expression was in positive correlation with the grade of an arteriolar hyalinosis. In patients who achieved partial or complete remmison, glomerular ET-1 expression appeared significantly lower compared to those patients who experienced stationar course or disease progression. CONCLUSION: glomerular ET-1 immunoexpression was significantly higher among patients with glomerulonephritides compared to the control group and influenced on the course of glomerulonephritis. This should be further investigated in future long-term prospective studies with larger number of patients.