Magnesium is one of the commonly used dietary supplements. Therefore, this study was to evaluate the content of short, medium and long-chain fatty acids and their esters in isolated rat hepatocytes induced by magnesium and/or ethanol. Isolation of hepatocytes was carried out by the Seglen's enzymatic method using collagenase. To thus prepared samples ethanol and/or MgCl2 solution were added, respectively, so that their concentrations were as follows: 150 mM/dm3 ethanol and/or 2 mM/dm3 MgCl2, 4 mM/dm3 MgCl2. The contents of short, medium and long-chain fatty acids and those of ester-bound acids were determined. The statistical evaluation of the experiment was made by comparing the area normalized for the analysed fatty acids in hepatocytes incubated for 5 h in the presence of the test substances. The effect of magnesium ions on the content of fatty acids and their esters in isolated hepatocytes incubated for 5 h depended on their concentration in the medium. A normalizing effect of magnesium ions on ethanol-induced changes in the content of C14-C17, C18-C20 and C21-C24 fatty acids was demonstrated. A normalizing effect of magnesium on ethanol-induced changes in the content of ester-bound fatty acids in hepatocytes was not confirmed.