Objective:To assess the effects of intranasal cortisteroids application on IL-5 expression in nasal polyps.Methods:Nasal polyps from topical nasal steroid treated patients (n=16) and untreated patients (n=16) were investigated.The specimens were stained by ABC immunohistochemical approach.Results:Most of the IL-5 positive cells were eosinophils,and there was a significant correlation of the mean IL-5 positive cell numbers with total (chromotrope 2R-positive) eosinophil numbers (y=14.782+2.002x,r=0.648,P＜0.01).Compared with untreated polyps,the steroid-treated polyps contained a slightly lower tissue density of IL-5 positive cells,and the difference was not statistically significant.Conclusions:Eosinophils are one of the origins of IL-5 synthesis.The treatment used here was insufficient to affect IL-5 expression in nasal polyps.