Brugada syndrome is associated with sudden cardiac death in patients with a structurally normal heart. The electrocardiogram (ECG) pattern of Brugada syndrome is characterised by complete or incomplete right bundle branch block and ST-segment elevation in the right precordial leads. These ECG signs may not always be apparent but can be unmasked with certain anti-arrhythmia agents. We report here a case of a 26-year-old woman without detectable structural heart disease but with a history of syncope, cardiac arrest, intubation and defibrillation for ventricular fibrillation. We performed challenge tests with propafenone and ajmaline. After infusion of propafenone, there were minimal ECG changes which were not diagnostic for Brugada syndrome. One week later the provocation test was repeated with ajmaline. During infusion of ajmaline, prominent J waves and ST-segment elevation appeared in the right precordial leads (V1-3). Premature ventricular complexes were seen on a 12-lead ECG. The patient's ECG showed Brugada type I pattern. She received an internal cardioverter/defibrillator and was discharged with a beta-blocker.