Twenty-two healthy males ranging in age between 18 and 43 years were studied by arterial blood sample obtained before nasal surgery and again after complete bilateral nasal obstruction produced by nasal packing. Five of these patients had a third sample drawn after pack removal. The pO2 dropped from a preoperative mean of 85 mm Hg to 74 mm Hg. This difference is statistically significant; pCO2 did not change between the two measurements. This result is attributed to hypoxia caused by acute total nasal obstruction. It suggests that anterior packing alone may cause a clinically important hypoxia in patients with inadequate pulmonary reserve and that these patients merit close observation when bilateral anterior packing is placed. The early removal of anterior packing in patients where possible seems indicated. Supplemental O2, (40 percent) for patients over 40 years of age requiring nasal packing is practiced at this Center.