BACKGROUND: Preoxygenation is routine prior to rapid sequence induction of general anesthesia for a cesarean section. The aim of this study was to evaluate the preoxygenation techniques of tidal volume breathing (TVB) and deep breathing (DB) for a cesarean section. METHODS: One hundred twenty ASA I and II patients scheduled for a cesarean section under general anesthesia participated in the study. Preoxygenation was performed with 5, 7, and 10 L/min 100% oxygen. The following techniques were tested: 1) normal TVB for a 5-min period (TVB/5 min) and 2) DB for a 2-min period (4 DB/0.5 min, 8 DB/min, 12 DB/1.5 min and 16 DB/2 min). Inspired (FIO2) and end-tidal oxygen fraction (FETO2), end-tidal carbon dioxide pressure (ETCO2) and oxygen saturation (SpO2) were measured at 0.5-min intervals. RESULTS: During TVB, FETO2 increased rapidly between 0.5 and 3.5 min and plateaued by 3.5 min at 78.5%, 83.3% and 90.8% with 5, 7 and 10 L/min 100% oxygen, respectively. Four DB/0.5 min increased FETO2 to 64.7%, 67.2% and 72.3% at 5, 7, and 10 L/min 100% oxygen, respectively. As compared with four DB/0.5 min, the values of FETO2 with TVB/1.5 min and TVB/2 min were high at 7, 10 and 5 L/min 100% oxygen. CONCLUSIONS: We concluded that TVB/2 min was more effective than four DB/0.5 min in achieving preoxygenation but eight DB/min could be used in case of an emergent operation.