Because anesthesia affects the integrity of the autonomic nervous system, anesthesiologists use vital signs to maintain respiratory and circulatory homeostasis. However, patients with genetic predispositions or with autonomic dysfunctions are at risk of severe complications from anesthesia. For these patients, the monitoring of vital signs may not give sufficient warning to avoid complications. The development of methods to measure autonomic tone could be of interest to anesthesiologists because they could warn of changes in autonomic tone before vital signs are affected. New noninvasive methods are being developed to obtain measurements of parasympathetic and sympathetic output allowing for the monitoring of perioperative autonomic tone. These measurements are based on analysis of heart rate and blood pressure variability. In this report, the principals of the analysis of heart rate and blood pressure variability will be explained and the usefulness of these methods to anesthesiologists will be discussed.