Enhanced renal sodium retention and potassium loss in patients with cirrhosis is due to activation of mineralocorticoid receptors (MRs). Increased aldosterone concentrations, however, do not entirely explain the activation of MR in cirrhosis. Here, we hypothesize that cortisol activates MRs in patients with cholestasis. We present evidence that access of cortisol to MRs is a result of bile acid-mediated inhibition of 11 beta-hydroxysteroid dehydrogenase type 2 (11 beta-HSD2), an MR-protecting enzyme that converts cortisol to cortisone. Twelve patients with biliary obstruction and high plasma bile acid levels were studied before and after removal of the obstruction. The urinary ratio of (tetrahydrocortisol + 5 alpha-tetrahydrocortisol)/tetrahydrocortisone, a measure of 11 beta-HSD2 activity, decreased from a median of 1.91 during biliary obstruction to 0.78 at 4 and 8 weeks after removal of the obstruction and normalization of plasma bile acid concentrations. In order to demonstrate that bile acids facilitate access of cortisol to the MR by inhibiting 11 beta-HSD2, an MR translocation assay was performed in HEK-293 cells transfected with human 11 beta-HSD2 and tagged MR. Increasing concentrations of chenodeoxycholic acid led to cortisol-induced nuclear translocation of MR. In conclusion, 11 beta-HSD2 activity is reduced in cholestasis, which results in MR activation by cortisol.