The objective of this study was to determine whether the allergy factor affects therapeutic response of nasal polyps. A total of 68 patients were enrolled between 1 October 1999 and 1 January 2002 at the Allergy and Rhinology Clinic, Faculty of Medicine, Songklanagarind Hospital. Allergy skin prick test was performed in order to divide patients into a positive skin test group and a negative skin test group. Their medical history was recorded including age, sex, nasal symptoms, concomitant diseases and medications. Patients in both groups were treated over a 6 week period with Budesonide nasal spray. Nasal symptoms, polyp size, nasal and oral expiratory peak flow were evaluated at each visit. Overall assessment of treatment efficacy was evaluated by patients at 3 and 6 weeks after treatment. The mean value of these variables during treatment and a baseline period were compared within and between groups. After 3 and 6 weeks of treatment of nasal polyps with topical Budesonide nasal spray, nasal symptoms, polyp size, nasal and oral expiratory peak flow index and overall response to treatment were improved within both groups. Comparing the two groups, there were greater improvements in the negative skin test group compared to the positive skin test group in all variables. These differences in variable scores between groups showed a tendency to increase overtime after treatment was terminated. The results demonstrate that nasal polyps with positive allergen skin test had less improvement compared to nasal polyps with negative allergen skin test in all nasal signs and symptoms and these differences in improvement showed a tendency to increase over time after treatment.