In a 38-year-old woman who was hospitalized because of hypertension and hypokalaemic alkalosis, the intake of liquorice (200 g per day) was proven to be the cause. A liquorice provocation test produced all the expected clinical and biochemical abnormalities. Some kinds of liquorice contain glycyrrhetic acid which inhibits the enzyme 11-beta-hydroxysteroid dehydrogenase (e.g. in the kidney) leading to decreased transformation of cortisol into cortisone. The mineralocorticoid action of cortisol causes a drop in serum potassium and an increase in serum sodium concentration, together with a metabolic alkalosis, which in the patient described led to retention of water resulting in weight increase and hypertension.