A 71-year-old woman was admitted with hypotension and bradycardia. An electrocardiogram showed flattened T waves and increased U wave prominence, resulting in a long QT(U) syndrome. Her initial serum potassium level was 1.6 mmol/L (all other electrolytes, including magnesium, were normal). She suffered recurrent ventricular tachycardia and ventricular fibrillation arrest requiring direct current cardioversion and high-dose intravenous potassium chloride replacement. Systematic enquiry revealed that she had been constipated for a number of months and had resorted to consuming large quantities of liquorice on a daily basis for its laxative effects. Endocrinology review identified no primary abnormality of the renin- angiotensin- aldosterone axis, and the patient was diagnosed with hypokalemia secondary to liquorice overindulgence. Liquorice has a mineralocorticoid effect. If chronically consumed in large quantities, this effect may lead to severe depletion of whole-body potassium stores. The present case highlights a rare but important cause of hypokalemic cardiac arrest of which all acute care physicians should be aware.