Two hours after taking 100 mg of flecainide, a patient developed gastrointestinal complaints, dizziness and shortness of breath. The ECG demonstrated novel prolonged JT interval with negative T wave in the precordial leads. During admission, several attacks of non-sustained ventricular tachycardia occurred. The plasma drug concentration was 814 mg/l. Although the tachycardia was non-sustained, cardiovascular collapse developed. Serum electrolytes were normal and myocardial infarction was excluded. The patient is now free of symptoms without medications.