The use of nasal spirometry as an objective measure of nasal septal deviation and the effectiveness of septal surgery Nasal spirometry, after decongestion, was used to assess the severity of septal deviation in 31 patients before and after nasal septal surgery. Patients were divided into two groups on the basis of their preoperative nasal partitioning of airflow ratio (NPR). The NPR ranges from 0.00 (equality of airflow) to 1.00 (total unilateral obstruction) with the normal range defined as 0.00–0.34. In 14 patients with a preoperative NPR within the normal range, the median NPR was not influenced by surgery (preop 0.14 to postop 0.12, P= 0.07). In 17 patients with a preoperative NPR outside the normal range, there was a significant reduction of the median NPR after surgery (preop 0.50 to postop 0.16, P < 0.01). The correlation of NPR with subjective assessment of the deviation was r = 0.85 (P < 0.01), and with patient subjective symptom assessment r= 0.94 (P < 0.01) preoperatively and r= 0.51 (P < 0.01) postoperatively. The findings indicate that nasal spirometry may be useful in patient selection for septal surgery.