The knowledge progressively accumulated on the relation between changes in autonomic activity and cardiac mortality, particularly in the setting of acute myocardial ischaemia, has turned during the last decade toward the potential prognostic value of markers of autonomic activity. Two of these markers, heart rate variability and baroreflex sensitivity, have gained progressive popularity. This chapter reviews some of the experimental observations that were instrumental for the novel clinical approach to post-myocardial infarction risk stratification based on the use of autonomic markers as risk stratifiers. It then focuses on clinical studies with special attention for a very recent multicentre prospective study (ATRAMI) carried out in almost 1300 post-myocardial infarction patients and aimed at the evaluation of the prognostic value of both heart rate variability and baroreflex sensitivity. Finally, some pathophysiological considerations are added to clarify the legitimacy, or lack of it, of the terminology currently used in clinical studies based on autonomic markers.