Nasal obstruction is predominantly a subjective patient complaint. Therefore there is wide variation in patients' interpretations of the symptom. History and physical examination are reasonable diagnostic indicators, but they are highly subjective, necessitating an objective means of evaluation. Rhinomanometry is a very useful tool for evaluating the degree of nasal obstruction, objectively. Nasal airway resistance was measured in 68 healthy adults, 68 healthy children, 80 patients with nasal obstruction before and after nasal surgery, 30 patients with allergic rhinitis, and in 50 patients with adenoid hypertrophy by active anterior rhinomanometry method using rhinomanometer. The results were as follows : 1) The mean total nasal resistance was 0.223 Pa/cm³/sec in the adult control group, 0.266 Pa/cm³/sec in the child control group, and 0.634 Pa/cm³/sec in the patient group. 2) In the normal adult control group, the mean total nasal resistance during inspiration was not significantly different from that during expiration(p>0.05). 3) In the normal child control group, the mean total nasal resistance of boys was not significantly different from that of girls, and diminished with increasing age. 4) The mean total nasal resistance of patients on whom nasal surgery was performed after schrinkage of nasal mucous membrane with ephedrine nasal spray was 0.433 Pa/cm³/sec and it was greater than that of the control adult group at 0.165 Pa/cm³/sec, with statistic significance(p<0.01). 5) In comparing the results of the rhinoscopic assessment with the subjective symptoms of the patient, there was a significant correlation between the narrow side and subjective obstruction(p<0.05). 6) Comparing the results of the rhinoscopic assessment with nasal resistance measurements, there was a significant correlation(p<0.05). In addition, unilateral nasal resistances of the narrow side and wide side were significantly different(p<0.001) than those values in the control group. 7) There was no significant difference(p>0.05) in the nasal resistance of the groups with mucosal and structural abnormalities before or after decongestion. Therefore, no clearcut distinction between the structural and mucosal causes of nasal obstruction could be made by rhinomanometry. 8) There was a significant correlation between the mean total nasal resistance and the patient's subjective assessment of nasal obstruction(p<0.01). 9) Compared with preoperative resistance after surgery, the mean total nasal resistance under decongestion was decreased from 0.433 Pa/cm³/sec to 0.275 Pa/cm³/sec with statistical significance(p<0.01). 10) The mean total nasal resistance after surgery in patients whose symptom of nasal obstruction was improved was reduced, but in patients whose symptom of nasal obstruction was not improved was slightly increased. 11) The mean total nasal resistance in allergic rhinitis patients was 0.515 Pa/cm³/sec and it was greater than that of the control group, with statistical significance(p<0.05). 12) The mean total nasal resistance of allergic rhinitis patients after medical treatment(ketotifen, astemizole) gradually decreased from the first week through the 6th week, and especially decreased during the initial two weeks, with statistical significance(p<0.05). 13) The mean total nasal resistance of adenoid hypertrophy patients was 0.442 Pa/cm³/sec(greater than that of the control child group), and it was reduced after operation(0.294 Pa/cm³/sec)(p<0.01). In conclusion, rhinomanometry can be useful in evaluating objectively the severity of nasal obstruction and the results of nasal surgery.