Disturbances of mineral metabolism are one of the many complications observed in patients with renal failure. Fluids used in dialysotherapy may introduce elements to a patient’s body. On the other hand, some trace elements may be removed. Dialysis fluids contain chlorides of calcium (Ca), magnesium (Mg), sodium (Na), and potassium (K), but they may also be contaminated by toxic metals. In the first part of our work the amounts of Mg, Ca, zinc (Zn), and iron (Fe) were determined in samples of hemodialysis fluids just before and after a dialyzer. The concentration of copper (Cu), aluminium (Al), lead (Pb), cadmium (Cd), and chromium (Cr) were measured by the atomic absorption spectrometry method (AAS) in a graphite furnace (GFAAS) in the same dialysates. The average concentration of Cu in dialysis fluids before and after dialyzer was 13.51 and 10.51 μg L-1 respectively, Al – 8.72 and 7.88 μg L-1, Pb – 24.03 and 22.81 μg L-1, Cd – 1.09 and 1.07 μg L-1, Cr – 5.91 and 6.28 μg L-1. Except for Cr (p < 0.05), the comparison of concentrations of all the measured elements before and after haemodialysis did not show any significant differences. Positive significant correlations between the element concentration before and after a dialyzer were found for Al (r = 0.33030 and Cd (r = 0.7496). In the samples of dialysis fluids of patients who had been dialyzed for less than one year, a negative balance of elements was found, except Pb. The balance was positive in patients who had been dialyzed for more than a year. Our findings also show statistically significant negative correlation between duration of dialysis treatments and Al concentration. Statistically, the examined dialysis fluids seem to be safe for dialyzed patients. However, individual data show that it is important to control elemental levels in dialyzates used for many years to prevent some complications in these patients.