The article reports that adverse reactions to drug therapy are the bane of the practitioner and all the more so when they occur in an idiosyncratic or apparently unpredictable, fashion. At baseline, risk factors for development of torsades de pointes in the present study were female gender, premature ventricular contractions and treatment with diuretics. The concept of repolarization reserve is also consistent with the notion of a genetic predisposition to torsades de pointes. The development of Torsades de pointes at low plasma quinidine concentrations may reflect the drug's multiple electrophysiological effects interacting with other risk factors as described below.