Aim: Longevity of peritoneal membrane is an important issue in patients treated with peritoneal dialysis (PD). In our study, we studied the impact of angiotensin receptor 1 (AGT R1) and aldosterone syn- thase (CYP11B2) gene polymorphism on peritoneal concentrations of interleukin-6 (PI-IL-6), vascular endothelial growth fac- tor (PI-VEGF), plasminogen activator in- hibitor-1 (PI-PAI-1), transforming growth factor-β (PI-TGF-β), and cancer antigen-125 (PI-CA-125) as known markers of perito- neal fibrosis. The single nucleotide polymor- phism rs5186 (A1166C) in AGT R1 gene is located in 3’ untranslated region (UTR) of the gene, while polymorphism rs1799998 (T -344 C) in CYP11B2 gene is located in the promoter region of the gene. Methods: We compared marker concentrations in patients with genotype DD vs. Dd and dd for AGT R1 and patients with genotype HH vs. Hh and hh for CYP11B2. Results: The results show that polymorphism of CYP11B2 gene is associat- ed with serum concentration of aldosterone. Patients with genotype HH had statistically significantly lower serum concentration of aldosterone (p = 0.04). These patients also showed a trend to a lower rate of production of I-IL-6 (p = 0.07), which correlated with lower concentrations of PAI-1 (p = 0.002) and VEGF (p = 0.005). AGT R1 gene poly- morphism did not show any association with studied variables. Conclusions: Our findings suggest the possibility of genetic predispo- sition for development of peritoneal fibrosis that could be important for identification of patients with an “unfavorable” genotype, which could lead to customized prescription of appropriate therapy and personalized pa- tient management.