In 5 healthy subjects and in 5 patients with decompensated liver diseases, the concentrations of cortisol, canrenone and canrenoate-K were determined after single doses and after a long-term treatment with spironolactone. The concentrations of the metabolites of spironolactone were determined fluorimetrically, those of cortisol by a highly specific radioimmunoassay with previous chromatographic separation. As a result, non-interaction between spironolactone medication and cortisol metabolism, even at high dose and long-term treatment conditions, was established neither in normal test subjects nor in patients with liver failure.