The majority of pediatric patients requiring surgery are monitored noninvasively. In the past 20 years these monitors have traditionally consisted of a precordial stethoscope, electrocardiogram (ECG), noninvasive blood pressure monitor, and temperature probe. Over the past decade, continuous pulse oximetry and end-tidal carbon dioxide (CO2) analysis have made a significant impact on routine noninvasive monitoring. Temperature assessment and end-tidal CO2monitoring are discussed separately in this issue. The purpose of this chapter is to detail the use of precordial and esophageal stethoscopes, discuss options for measuring blood pressure noninvasively, and review the value of continuous electrocardiography and pulse oximetry in pediatric anesthesia. For most institutions these monitors form the first line of defense against an anesthetic mishap and provide assurance of adequate patient care.