BACKGROUND AND OBJECTIVES: Allergic rhinitis is one of the most common allergic diseases. Diagnosis and therapeutic improvement of allergic rhinitis have been evaluated using only subjective symptoms. However, it is important to assess nasal obstruction using objective parameters for the diagnosis and evaluation of therapeutic responses. The aim of this study was to evaluate the usefulness of the objective parameter for nasal obstruction: nasal airway conductance using rhinomanometry to diagnose allergic rhinitis by allergen specific nasal challenge test. SUBJECTS AND METHODS: A total of 56 individuals were included in this study. They were categorized into a patient group sensitized to house dust mite (n=32) and a control group (n=24). They responded to the questionnaire concerned on rhinitis symptoms, and underwent skin prick tests to 11 common inhalant allergens and Dermatophagoides pteronyssinus(D.P.)- specific nasal provocation tests with varying degrees of concentrations. Symptom scores based on subjective nasal symptoms such as runny nose, sneezing, nasal obstruction, and visual analogue scale (VAS) were recorded. Objective parameter i.e. nasal airway conductance using rhinomanometry was also measured before and after the inhalation of D.P. aerosol. RESULTS: Nine subjects of the patient group (28.1%) experienced sneezing, 12 (37.5%) rhinorrhea, 17 (53.1%) nasal obstruction, and 9 (32%) nasal or ocular itching. There were no significant differences between the patient and the control groups in baseline nasal conductance measured by anterior rhinomanometry (p>0.05). In the patient group, however, nasal conductance was significantly decreased after inhalation of the low D.P. concentration (250 B.E.U. of D.P. extract) compared to baseline value (p<0.05), while in the control group, the nasal conductance showed no significant differences after the inhalation of D.P. aerosol(p>0.05). Symptom scores were more significantly increased in the high D.P. concentration (1000 B.E.U. of D.P. extract) than in the baseline concentration of the patient group (p<0.05), but the control group revealed no differences (p>0.05). As for VAS, the patient group showed significant differences after the high D.P.(5000 B.E.U. of D.P. extract) inhalation (p<0.05), while the control group showed no difference. CONCLUSION: Although nasal symptoms such as obstruction, itching, sneezing, and rhinorrhea should be considered in diagnosing allergic rhinitis, nasal conductance using rhinomanometry can be a more valuable objective index since it can discriminate the patient group from the control group more sensitively in lower allergen concentrations.