Acoustic rhinometry, which is based on the reflection of acoustic signal entering the nasal cavity, is a new method introduced to assess the geometry of the nasal cavity. We evaluated the mean value change of the minimal cross-sectional area(MCA) and the volume of the nasal cavity, before and after septoturbinoplasty. A group of 40 patients with septal deviation was examined with acoustic rhinometry preoperatively and postoperatively between August 1994 and May 1995. These values were compared with those of 17 normal control subjects. The results were as follows : 1) The minimal cross-sectional area(MCA) in control group was 0.53cm² before decongestion and 0.62cm² after decongestion(p>0.05). The volume in control group was 7.5cm² before decongestion and 10.26cm² after decongestion(p<0.05). 2) Acoustic rhinometric patterns were classified into two patterns(W and C patterns) according to existence of C notch. The most common acoustic rhinometric pattern in control group was W patterns(14cases) except C patterns(3 cases). 3) The minimal cross-sectional area(MCA) in patient group was 0.44cm² preoperatively and 0.62cm² postoperativrly(p<0.05). The nasal volume was 6.21cm³ preoperatively and 8.06cm³ postopertively(p<0.05). 4) The patient group(40cases) was divided two patterns(31C patterns and 9W patterns). W patterns were statistically significant in minimal cross-sectional area(MCA) and volume preoperatively except C patterns. 5) The postoperative MCA of satisfactory patient group(0.47cm²) was larger than that of unsatisfactory patient group(0.29cm²) and statistically significant(p<0.05). A highly significant relationship between MCA and the subjective feeling of nasal patency, before and after surgery, suggests that MCA is a valuable parameter to express nasal patency. Acoustic rhinometry seems very suitable for evaluation of the nasal cavity in cases where septoturbinoplasty considered, as well as for postoperative evaluation.