A 47-year-old woman suffered from recurrent attacks of ventricular tachycardia. Her electrocardiogram showed low voltage, right bundle branch block and prolonged QT interval. Hormonal studies disclosed primary hypothyroidism. The arrhythmia responded to treatment with procainamide and did not recur following thyroid replacement therapy. The QT interval returned to normal. Five similar cases reported in the literature are reviewed, emphasizing the importance of QT prolongation, in the context of hypothyroidism, as a risk factor for the occurrence of ventricular tachycardia.