For diagnosis of perennial allergic rhinitis, varions kinds of diagnostic procedures are available, such as characteristic history, physical examination, X-ray, eosinophil in nasal secretion, blood eosinophil, serum IgE level, skin test, nasal provocation test and RAST. Among these, serum IgE level, skin test and RAST have important role in confirming the allergic diseases. Moreover, serum IgE is a main immunoglobulin in type I hypevsensitivity reaction which includes allergic rhinitis. To evaluate the diagnostic significance of serum IgE level in perennial allergic rhinitis, a clinical study was done with 107 cases of perennial allergic rhinitis pts. who were diagnosed by means of history, physical examination and skin test in Seoul National University Hospital during a period from Jan. 1980 to Sept. 1980. The results are as follows; 1) Serum IgE level has statistical significance under 29 years of age, but no statistical significance over 30 years of age. 2) The principal offending allergens of perennial allergic rhinitis are Dermatophagoides farinae, Dermatophagoides pteronyssinus, animal hair, house dust, silk under 29 years of age, and Rhizopus nigricans, Dermatophagoides pteronyssinus, Dermatophagoides farinae, house dust, silk, staphylococcus aureus over 30 years of age. 3) Blood eosinophilia has no significance in the diagnosis of perennial allergic rhinitis and no significant relation-ships to serum IgE level. 4) Nasal secretion eosinophilia is more common under 29 years of age than the group over 30 years of age, but no significant statistical relationship to serum IgE level.