To critically and systematically review the data available on the sinonasal application of nasal nitric oxide measurement, particularly its use as a diagnostic, prognostic, or treatment effect indicator. EMBASE 1980 to February 10, 2010; Medline 1950 to February 10, 2010; Cochrane Collaboration database; NHS Evidence Health Information Resources database. Review Methods. The databases were searched using a search strategy designed to include manuscripts relevant both to nitric oxide measurement and sinus or nasal problems. A title search was carried out on these manuscripts to select those relevant to clinical or basic science aspects of nitric oxide measurement. A subsequent abstract search selected those manuscripts concerning the application of nitric oxide measurement to sinonasal problems. The manuscripts selected were subject to a full-text review to extract data sets of nasal nitric oxide readings for different patient groups. Initially, 1088 manuscripts were selected. A title search found 335 manuscripts of basic scientific or clinical interest. An abstract search found 35 manuscripts directly relating to nitric oxide measurement in sinonasal disease. Full-text analysis produced 20 studies with extractable data on nasal nitric oxide levels in clearly defined patient groups. Studies did not show sufficient homogeneity to enable substantial meta-analysis of aggregated data. Current evidence shows that nasal nitric oxide is not a clinically useful measure for sinonasal disease. Although there is some evidence that sinus surgery is associated with lowered nasal nitric oxide levels, there is no evidence that this is associated with deterioration in sinus health.