This study was designed to validate and standardize a method for unilateral nasal nitric oxide (NO) measurement. Fourteen healthy volunteers and 11 patients who had undergone unilateral medial maxillectomy were enrolled. Nasal NO was measured unilaterally by means of a dual pump system, and bilateral nasal NO was measured by aspirating air through the nasal airway in series. The median unilateral NO output was 195 nL/min on the surgical side and 291 nL/min on the contralateral, surgically untreated side (p = .006). The NO output was not significantly different between nostrils in the control group (p = .82). With the bilateral technique, there was no significant difference between the surgery group and the healthy-subjects group (p = .72). The unilateral nasal NO technique is sensitive in determining unilateral differences in nasal NO production. The NO outputs from the nostrils were similar in normal subjects regardless of the nasal cycle, but were significantly lower on the operated side in the unilateral nasal surgery group.