Infants and children undergoing upper intestinal endoscopy were monitored by both pulse oximetry and chest EKG. Fifty-seven patients between the ages of 6 weeks and 36 months underwent 60 flexible upper intestinal endoscopies. All patients received parenteral sedation only. All procedures were successfully performed without significant complications. In 53 of the patients there was only transient mild oxygen desaturation with introduction of the endoscope into the pharynx and upper esophagus. In contrast, in seven patients, oxygen desaturation to less than 90% was noted following sedation but prior to insertion of the endoscope without overt clinical evidence of complications. Oxygen administered by nasal cannula resulted in a return of the oxygen saturation to at least the preprocedural level and allowed for safe completion of the studies. With improved monitoring, the use of smaller, more flexible endoscopes, and more experience, routine general anesthesia in children <3 years of age, as recommended in the past, may not be mandatory. Pulse oximetry may be particularly useful as an early indicator of poor oxygenation and may provide an objective means to assess the need for supplemental oxygen and to determine the degree of postprocedural observation.