Ketotifen(Zaditen^®) is an oral drug which acts antianaphylactic and antihistamine reactions, so available for reducing bronchial asthma attack and the use of steroid and bronchodilators. Authors studied clinical effect and side effect of ketotifen in 35 patients composed of 20 patients diagnosed as allergic rhinitis and 10 patients diagnosed as vasomotor rhinitis with no allergen identified and 5 patients with poor result after hyposensitization therapy. The results are as following ; 1) Thirty-five patients, 25 adults(male : famale = 3 : 2) and 10 children(male : female = 7 : 3) were included in this study. Therapeutic period was at least 8 seeks and, case by case, prolonged to 12 weeks, and average therapeutic period was 9.14 weeks. Ketotifen 1mg was orally given twice a day to adult patients, and in children, 2~5ml of Zaditen^® syrup(0.4~1.0mg of ketotifen) was orally given twice a day according to their age. 2) Clinical effects were obtained as following ; In case of allergic rhinitis(20 cases), much improved in 6 cases(30.0%), improved in 9 cases(45.0%), less improved in 3 cases(15.0%), not improved in 2 cases(10.0%) ; In case of vasomotor rhinitis(10 cases), much improved in 4 cases(40.0%), improved in 3 cases(30.0%), less improved in 1 case(10.0%), not improved in 2 cases(20.0%) ; In case of no response to previous hyposensitization therapy(5 cases), improved in 4 cases(80.0%), not improved in 1 case(20.0%). 3) In allergic rhinitis group, skin test and eosinophil count in nasal smear were studied after treatment. In skin test, erythema and wheal were disappeared in 6 cases(24.0%) and reduced in size in 11 cases(44.0%). In eosinophil count, eosinophils in nasal smear were disappeared in 10 cases(40.0%) and reduced in number in 9 cases(36.0%). 4) For objective evaluation of nasal airway resistance after ketotifen treatment, anterior rhinometer was used. The mean nasal airway resistance after ketotifen treatment, 0.395 Pa/cm³/sec(SD±0.120), was lesser than that before treatment, 0.496 Pa/com³/sec(SD±0.172). There was statistically significant difference in the mean total nasal airway resistance(p<0.01). 5) Side effect of ketotifen was observed only in two patients with mild transient sedation, but no other side effect enough to hold the medication was observed. 6) There were no significant changes in CBC, RUA, liver function test after this study. Reviewing the results, ketotifen is suggested to be an effective drug for allergic rhinitis and vasomotor rhinitis.