High concentration of intraerythrocyte ATP is a common phenomenon in patients with chronic renal failure (CRF). It is likely that this is a result of increased plasma concentration of adenine--one of purine moiety donors which is necessary for ATP synthesis. In the present study we monitored changes of both adenine and intraerythrocyte ATP concentration during renal replacement therapy. We have also estimated the influence of erythropoietin treatment. 4 groups of patients were included into the study: 22 patients with CRF, 22 patients on maintenance hemodialysis treatment (11 patients with EPO therapy), 19 patients after kidney transplantation (7 patients with insufficiency of transplanted kidney) and 26 healthy volunteers served as a control group. The measurements were performed in plasma and erythrocyte extracts using HPLC. Significant decrease of high plasma adenine concentration was observed after both HD session and successful kidney transplantation, however the achieved values were still higher than in healthy volunteers. Kidney transplantation resulted in a permanent decrease of plasma adenine concentration, but along with the deterioration of transplanted kidney function, the plasma adenine concentration reincreased. Also, it started to increase right after HD session had ended. On the other hand, the intraerythrocyte concentration of adenine and ATP after successful kidney transplantation and single HD session came back to normal values. Also in this case, along with the deterioration of transplanted kidney function, both studied parameters reincreased. We have not observed any significant influence of erythropoietin treatment on studied adenine nucleotide concentration in hemodialysis patients. The present study confirms the strong interrelationship between the adenine nucleotide metabolism abnormalities and the advancement of renal failure. The abnormalities intensify along with the disease progression and the renal replacement therapy results in partial their correction.