Given the rarity of antipsychotic drug-associated polymorphic ventricular tachycardia, case reports rather than studies such as ZODIAC will give us the most information about this adverse event. Papers analyzing case reports (4, 5) emphasize that nondrug risk factors for QTc interval prolongation are invariably present in reports of next-generation antipsychotic drug-associated QTc interval prolongation, polymorphic ventricular tachycardia, torsade de pointes, and cardiac death. Such risk factors include hypokalemia, hypomagnesemia, hypocalcemia, bradycardia, preexisting cardiovascular disease, congenital QTc interval prolongation, female sex, advancing age, baseline QTc interval prolongation, and coadministration of nonpsychotropic drugs associated with QTc interval prolongation. Studies attempting to identify next-generation antipsychotic drugs as a cause of QTc interval prolongation must have sufficiently complete data to identify the risk factors listed above. Perhaps Strom et al. (1) might review the case reports of ziprasidone-associated QTc interval prolongation and cardiac arrhythmias on file at Pfizer with this strategy in mind.