In literature of the recent years, more and more attention has been paid to the correlations between magnesium and blood lipids. Lipid balance disorders induced by hypomagnesaemia bring about changes in the liquidity of cellular membranes. Increased migrationof lipids, in particular of VLDL and LDL, across arterial walls has been observed in hypomagnesaemia, with their consequential deposition in the internal membrane. Kidneys, apart from urine production and elimination, fulfil many other important functions in organism. They determine normal functioning of the whole organism, while disorders in their function lead to serious changes in homeostasis. Lipid balance disorders are a serious risk factorin the development of atherosclerotic lesions in patients with chronic kidney failure. The aim of this study was to examine the correlations between magnesium concentration and total cholesterol and HDL- and LDL-cholesterol contents in women and men with chronic kidney failure under and over 50 years of age. Subjects were divided into four groups: K1 – 14 women 34-50 years old, K2 – 14 women over 50 years old, M1 – 17 men 30-50 years old, and M2 – 13 men over 50 years old. Tests were made using a COBAS INTEGRA analyser. High concentration of Mg, exceeding the upper limit of reference values, was observed both in two women and men groups (K1 – 1.26 mmol(+) kg–1; K2 –1.25 mmol(+) kg–1; M1 – 1.13 mmol(+) kg–1; M2 – 1.16 mmol(+) kg–1). Also the levels oftotal and HDL-cholesterol in all subjects were within physiological limits (respectively: K1– 4.61 and 1.23 mmol(+) kg–1; K2 – 4.69 and 1.29 mmol(+) kg–1; M1 –3.94 and 1.20 mmol(+)kg–1; M2 – 3.98 and 1.16 mmol(+) kg–1). Only the LDL-cholesterol concentration in the group of younger men was below normal limit (1.93 mmol(+) kg–1). Small positive correlations were obtained between Mg content and that of total and LDL-cholesterol in older women and younger men groups as well as between Mg and HDL-cholesterol contents in both men groups. At the same time, a small negative correlation was obtained between Mg and LDL-cholesterol concentrations in the older men group. These correlations were statistically non-significant.