Patient monitoring is fundamental to the job of the anesthesiologist. Anesthetic drugs and surgical procedures can produce rapid changes in patient physiology and these changes may last throughout the perioperative period. It is essential that anesthesiologists have the capability to monitor these changes in real time to optimize patient safety and care throughout the perioperative period. The information acquired via various monitoring devices can be used to maintain quality patient care, but it does not guarantee any particular outcome. Multiple medical societies, including the preeminent anesthesiology society the American Society of Anesthesiologists (ASA), have agreed upon a standard set of monitoring devices referred to as the ASA standard monitors. Other monitoring devices and invasive monitoring methods may be used, in addition to the standard ASA monitors, depending on specific patient and intraoperative surgical concerns. It is important that anesthesiologists are aware of the variety of devices at their disposal, so that they may appropriately utilize those monitors to optimize and ensure quality patient care.