Background: It has been recently suggested that the presence of the methylenetetrahydrofolate reductase gene 677TT genotype is associated with younger age at initiation of dialysis, thus raising a hypothesis that younger renal patients carrying the TT genotype are at higher risk to develop end-stage renal disease. The aim of this study was to test the association between the C677T polymorphism and the presence of end-stage renal disease using a family-based study design. Material and Method: C677T polymorphism was genotyped in a group of 247 family trios (offspring affected with end-stage renal disease, dialysed or conservatively treated, and both parents). Transmission/disequilibrium test (TDT) was used to evaluate allele transmission from heterozygous parents to affected offspring. Results: The TDT analysis revealed no significant deviation in the transmission of the MTHFR C677T alleles to CRF patients (51 vs. 49% for the C allele and T allele transmission, respectively). We observed a significant relationship between MTHFR genotypes and total plasma homocysteine (tHcy), as well as folate concentration. Also, plasma tHcy and folate were negatively correlated. Conclusion: Our results did not show any association between the MTHFR reductase C677T polymorphism and the increased risk of the development of end-stage renal disease. Whether this polymorphism contributes to the faster rate of decline of renal function in renal patients, must be evaluated further.