The pathogenesis of pseudohyperaldosteronism from licorice has been evaluated in 6 male volunteers taking daily 7 g of a commercial preparation of licorice for 7 days, corresponding to an intake of 500 mg/day of glycyrrhizic acid. Pseudohyperaldosteronism was evident during the treatment (increase of body weight, suppression of plasma renin activity and plasma aldosterone, reduction of serum potassium). The ratio (tetrahydrocortisol + allo tetrahydrocortisol)/tetrahydrocortisone in urine increased in 5 cases after 3 days of treatment, without an increase of plasma mineralocorticoid activity (PMA). In the 6th case the urinary ratio was unchanged and PMA increased from the pretreatment value. After 7 days of therapy the ratio remained high and PMA was not measurable in 3 cases, while in the other 3 cases the ratio returned to pretreatment and PMA was higher than pretreatment value. We conclude that the pseudohyperaldosteronism from licorice is initially related to decreased activity of 11 beta-hydroxysteroid-dehydrogenase and afterwards also a direct effect of licorice derivatives on mineralocorticoid receptors becomes evident in some cases. In other cases however the effect on the enzyme is prevailing probably due to individual factors.