Allergic rhinitis is characterized by nasal hyperreactivity and inflammation of the nasal mucosa. Histological examination of the nasal mucosa in patients with allergic rhinitis has shown the significant infiltration of eosinophils. Four major proteins are found in eosinophil granules, namely eosinophil cationic protein(ECP), major basic protein(MBP), eosinophil peroxidase(EPO), and eosinophil-derived neurotoxin(EDN). After stimulation of the eosinophil, these protein granules are released and may cause damage to the surrounding cells and tissues. EG2, which recognizes the cleaved and secreted form of ECP representing ""activated"" eosinophil, is able to be detected by the immunohistochemical techniques. Although the characteristics of these proteins concerning tissue damage in the local site of type I allergic reaction has been investigated mainly in the lower respiratory tract, the actual clinico-pathological role of these proteins in nasal allergies is not clear. In this report, we studied whether EG2 positive cell counts were correlated with the severity of clinical symptoms and nasal hyperreactivity. Subjects were 21 patients with allergic rhinitis ranging in age from 15 to 46 years old and 10 patients of a control group ranging in age from 18 to 50 years old. The results obtained were as follows : 1) In patients of allergic rhinitis, many EG2 positive cells were detected, mainly in the epithelial layer and in the superficial submucosal layer. However, in the control group EG2 positive cells were hardly found. 2) There was a significant correlation between EG2 positive cell counts and the severity of clinical nasal symptoms, especially the degree of nasal obstruction(r=0.67, p<0.01). 3) There was a significant correlation between EG2 positive cell counts and the sensitivity of nasal mucosa to histamine(r=-0.74, p<0.01). 4) There was a significant correlation between EG2 positive cell counts and degree of desquamation of the nasal mucosa epithelium(r=0.61, p<0.01). These results suggest that eosinophil activation may be related to the pathogenesis of nasal hyperreactivity.