Introduction: Recent guidelines recommend routine pulse oximetric monitoring during endoscopy, however, this has not been the common practice yet in the majority of the local endoscopic units. Aims: To draw attention to the importance of the routine use of pulse oximetric recording during endoscopy. Method: A prospective multicenter study was performed with the participation of 11 gastrointestinal endoscopic units. Data of pulse oximetric monitoring of 1249 endoscopic investigations were evaluated, of which 1183 were carried out with and 66 without sedation. Results: Oxygen saturation less than 90% was observed in 239 cases corresponding to 19.1% of all cases. It occurred most often during endoscopic retrograde cholangiopancreatography (31.2%) and proximal enteroscopy (20%). Procedure-related risk factors proved to be the long duration of the investigation, premedication with pethidine (31.3%), and combined sedoanalgesia with pethidine and midazolam (34.38%). The age over 60 years, obesity, consumption of hypnotics or sedatives, severe cardiopulmonary state, and risk factor scores III and IV of the American Society of Anestwere found as patient-related risk factors. Conclusion: To increase the safety of patients undergoing endoscopic investigation, pulse oximeter and oxygen supplementation should be the standard requirement in all of the endoscopic investigation rooms. Pulse oximetric monitoring is advised routinely during endoscopy with special regard to the risk factors of hypoxemia. Orv. Hetil., 2013, 154, 825–833.