Recently hyperreactivity of the nasal mucosa is accepted as the possible mechanism of nasal allergy and is understood as the local reaction due to increased sensitivity of effector cells, increased secretion of neurotransmitters and chemical mediators, and increased number or size of secretory cells. Clinical symptoms of nasal allergy are correlated with the sensitivity of nasal mucosa to histamine, chemical mediator. To understand hyperreactivity of nasal mucosa and as the preliminary clinical study for the histochemical study of nasal mucosa in patients with allergic rhinitis, we studied histamine sensitivity of nasal mucosa according to the degree of symptoms and duration of disease. Our results were as follows ; 1) Significant correlation between the duration of disease and symptom score was noted. 2) Significant correlation between the duration of disease and histamine threshold was noted. 3) Wider distribution of histamine threshold in patients with perennial allergic rhinitis than in controls was noted.