BACKGROUND: Eosinophils are suggested to play a deleterious role in the inflammatory disease of the respiratory mucosa by releasing granule substances such as major basic prorein and eosinophil cationic protein. To investigate the contribution of eosinophils in the pathogenesis of nasal polyps and the mechanism of their accumulation and activation, we observed the eosinophil inhllration and expression of endotjelial and epithelial cell adhesion molecules in the nasal polyp tissues. MATERIALS AND METHODS: Polyp and inferior turbinate mueosal specimens (polyp group) taken out of 20 patients and 10 inferior turbinate mucosa specimens of non-allergic and non-infectious controls (control group) were immunohistochemically stained using EG1, EG2, and mAb for the ICAM-1, VCAM-1 and E-seleetin. The number of EG1 (+) and EG2 (+) cells within lmm2 of tissue and the expression of ICAM-1, VCAM-1 and E-seleetin on the vessels (% of total vessel) and epithelial eelis (area x intensity) were compared among three groups. RESULTS:The inferior turbinate mucosae of nasal polyp patients .were infiltrated by signifieantly higher number of eosinophils (EG1:17, EG2:16/mm2) compared with those of controls (EGi:0, EG2:0/mm2) (p<0.05), and the polyp tissue revealed much more eosinophils (EG1: 213, EG2:154/mm2) than inferior turbinates of same patients and those of controls (p<0.001). ICAM-1 expression in the vessels was frequenly observed both in polyps and in the turbinate mucosae with significant difference (median:85% vs. 67%, p<0.05), and ICAM-1 expression in the epithelial ceils was significantly different between the polyp and turbinate groups (median:9 vs. 2.5, p<0. 01). VCAM-1 was moderately expressed on the vessels of both polyps and turbinate mucosac (median:37%, 14%, respectively) and their expressions were significantly different (p<0.01). E-selectin expression was moderate to low both in the polyps and in the turbinate mucosae (median:18%, 10% respectively) and their expressions were not significantly different (p>0.05). CONCLUSION: Most of the eosinophils infiltrated into nasal tissue as well as nasal polyps were activated forms and they were significantly increased in the nasal polyps compared to the inferior turbinate mueosae of the same patients and control subjects. Significantly increased expression of ICAM-1 and VCAM-1 on the vessels and increased epithelial ICAM-1 expression in the nasal polyps indicate that interactions of eosinophils with ICAM-1 and VCAM-1 participate in the pathogenesis of nasal polyps.