The aim of the study was obtain answers the following questions: 1. Are serum cadmium concentrations in patients with chronic renal failure (CRF) different from levels in healthy subjects? 2. Are serum concentrations of above mentioned metal different between haemodialysed and non-haemodialysed patients. 3. Are serum cadmium concentrations changing during haemodialysis? 66 patients with chronic renal failure (42 patients treated with haemodialysis and 24 non-haemodialysed patients) and 16 healthy subjects were observed. The blood samples in non-haemodialysed patients and healthy subjects were withdrawn only after cannula had been inserted into the antebrachial vein. The blood samples in haemodialysed patients were withdrawn four times: just before dialysis, during haemodialysis (in one hour of dialysis just in front of dialyser and just behind one) and after haemodialysis. Cadmium concentrations in serum in all examined group and cadmium concentrations in dialysis fluid and in demineralised water were measured by flame atomic absorption spectrophotometry. No significant changes were observed in serum cadmium concentration between patients with CRF and healthy subjects. Cadmium-concentration in non-haemodialysed patients was significantly higher than in haemodialysed patients. During haemodialysis a significant increase of serum cadmium level was observed. CONCLUSIONS 1. Serum cadmium concentration in patients with CRF and in healthy subjects are not statistically different; 2. No significant changes in cadmium concentration between uraemic group patients were found; 3. Haemodialysis influences significantly on cadmium concentration.