Background: Pulse oximetry has been recommended as a standard of care for ICU, CCU, Post Anesthetic Care Unit as well as general anesthesia. The device provides valuable data regarding blood oxygenation. But there are some limitations and inaccuracies of pulse oximetry. The purpose of the present study is to assess the knowledge of pulse oximetry in the doctors and nurses who frequently use pulse oximeter in their practice. Methods: We investigated 29 doctors(resident) and 41 nurses who answered a structured questionnaire about pulse oximetry. Questions were given about the knowledge of equipment, factors affecting readings, normal values in various patients, values in hypothetical clinical situations, education experience and source of information about pulse oximetry. Results: Only 20% of doctors understood how a pulse oximeter worked and about 60% of doctors and 80% of nurses were confused about factors influencing readings. About 30% of doctors and 12% of nurses had received formal training about the pulse oximetry. Sources of information about pulse oximetry were operating manual, senior, books and joumal. Conclusion: Our survey revealed that most of resident doctors and nurses using pulse oximeter were untrained, lacked knowledge of the basic principles and factors influencing saturation values in pulse oximetry. Therefore the systematic training program is important for doctors and nurses to use of pulse oximeter.(Korean J Anesthesiol 1996; 31: 791-796)