We evaluated the clinical and pathophysiological efficacy of hyposensitization with house dust extracts to perennial nasal allergy. Fifty-one patients with allergic perennial rhinitis completed 5 months to 15 years with a mean of 2.4 years course of hyposensitization treatment with house dust extracts, and analyzed clinical symptoms, nasal provocation testing, nasal hypersensitivity to histamine, mast cells and eosinophils in nasal scraping, specific IgG and IgG4 antibody in serum, and blood eosinophils and basophils in relation to therapeutic duration. The improvement in nasal symptoms was found in 74.1% in adults and 66.7% in child and the continuation of hyposensitization with house dust extracts for a half to one year showed significant improvement of clinical symptoms. In objective examination, nasal provocation testing, nasal hypersensitivity to histamine, the number of mast cells and eosinophils in nasal scraping, and blood basophils showed significant improvement at 6 to 12 months the same as clinical symptoms. These findings suggest that the continuation of hyposensitization with house dust extracts is recommendable as a basic treatment against perennial nasal allergy.