Methadone is known to prolong the QT interval and precipitate torsades de pointes. A 54-year-old prescription methadone user with hypokalaemia was referred to Critical Care with acute confusion and respiratory distress. Alcohol withdrawal was the presumed precipitant. The real precipitant only became evident on analysis of a 24-h ECG (Holter monitor) attached to the patient at the time. The patient had suffered prolonged (10 min) ventricular arrhythmias including torsades de pointes and self-terminating ventricular fibrillation. The patient made a full recovery. Risk factors for acquired long QT syndrome and the treatment of torsades de pointes are discussed.