Normal sleep is associated with slowing of the heart rate and occasional asymptomatic selflimited rhythm disturbances. Obstructive sleep apnea produces cyclical changes in heart rate and an increase in the occurrence of cardiac dysrhythmias. Sleep medicine practitioners should be familiar with routine methods, limitations, and scoring of cardiac events, including sinus tachycardia, sinus bradycardia, narrow and wide complex tachycardias, atrial fibrillation, and cardiac asystole. Other cardiac rhythms that are recognizable within the context of the sleep study should be reported. Changes in cardiac rhythm during polysomnography seldom result in adverse outcomes. Decisions regarding interventions for identified cardiac rhythms should be influenced by the nature of the dysrhythmia, risks identified by patient characteristics and comorbidities, and prevailing patient care strategies in managing heart disease.