This report describes a 64 year-old female patient admitted to our department for recurrent and symptomatic episodes of atrial fibrillation. Antiarrhythmic therapy with sotalol at 240 mg/day was started, and after 48 h the patient experienced several episodes of sustained torsade de pointes, dramatic marked QT interval prolongation and negative T wave, in absence of overt cardiac disease, renal failure, electrolyte abnormalities or baseline QT interval prolongation. This case emphasizes the importance of hospitalization at the starting of sotalol therapy, especially in female patients, even in absence of predisposing factors for drug-induced tachyarrhythmias.