BACKGROUND Hypoxia may occur in children undergoing upper digestive endoscopy under sedation. The purpose of this study was to compare the occurrence of desaturation during intravenous sedation with that which occurs during general anesthesia. METHODS Thirty-six patients between 3 months and 6 years old underwent a diagnostic esophagogastroduodenoscopy under sedation (n = 18) or general anesthesia (n = 18). Oxygen pulse oximetry, heart rate, and mean arterial pressure were monitored throughout the procedure. At the end of the procedure, the operator gave the value of the endoscopy satisfaction score on a scale of I (very good conditions) to IV (impossible procedure). RESULTS The minimum oxygen pulse oximetry value was significantly lower in the sedation group compared with that in the general anesthesia group (89 +/- 5 vs. 97 +/- 1; p < 0.001). In the general anesthesia group, the oxygen pulse oximetry level declined to less than 95% in only one child; but in the sedation group, it declined to less than 95% in 16 patients (5.5% vs. 89%). Nine patients had a profound desaturation in sedation group (oxygen pulse oximetry < 90%); no patients in the general anesthesia group had desaturation (50% vs. 0%). In the general anesthesia group, heart rate and mean arterial pressure remained stable during the whole procedure, whereas in the sedation group, heart rate and mean arterial pressure increased significantly during the procedure. The endoscopy satisfaction score was I in all 18 patients in the general anesthesia group, whereas in the sedation group, it was I in only 2 patients, II in 8 patients, and III in 10 patients. CONCLUSIONS These results confirm that hypoxia during upper digestive endoscopy in patients under sedation is a frequent occurrence in children. When compared with sedation, general anesthesia is a safer technique that prevents hypoxia and allows the gastroenterologist to perform the endoscopy under better conditions.