The chapter Rhythm and Conduction Disturbances in Stress Testing reviews the frequency and significance of arrhythmias and conduction abnormalities precipitated by exercise. Case examples are provided. PVCs occurring prior to, during exercise, or during recovery all modestly increase the risk of all-cause mortality in patients with and without known coronary artery disease (CAD). Ventricular tachycardia and premature ventricular complexes are often not reproducible on a subsequent exercise test. Exercise induced left bundle branch block (LBBB) predicts increased risk of the presence of CAD, all cause mortality, and often permanent LBBB. Differentiating wide complex tachycardia during exercise testing between supraventricular tachycardia and ventricular tachycardia can be challenging. The Wellens, Brugada, and Vereckei algorithms to distinguish between these arrhythmias are detailed and compared.