This guidance describes a nonclinical testing strategy for assessing the potential of a test substance to delay ventricular repolarization. The guidance includes information concerning nonclinical assays and integrated risk assessments. The assessment of the effects of pharmaceuticals on ventricular repolarization and proarrhythmic risk is the subject of active investigation. When additional data (nonclinical and clinical) are accumulated in the future, they will be evaluated and this guidance might be revised.