Immunohistochemical stainings were performed on polyp specimens of 48 patients and on mucosal biopsy specimens of the middle and inferior turbinates of 23 and 28 patients, respectively. Significantly more CD8+ (suppressor/cytotoxic) than CD4+ (helper/inducer) cells were found in the polyps. The number of CD2+, CD4+, and CD8+ lymphocytes in nasal polyps were very similar to the number in the macroscopically unaffected mucosa of the middle turbinates, whereas scores in the inferior turbinates were lower. In healthy subjects, the differences were smaller. CD22+ B cells were detected in varying numbers in the polyps in more or less organized clusters. Significantly more HLA-DR+ cells were found in polyps and middle turbinates than in the inferior turbinates. Eosinophils were found in moderate to large numbers in polyps of 77% of the patients. Mast cells and plasma cells were detected in moderate numbers, whereas neutrophils were found in 35% of the patients. In the middle and inferior turbinates varying but small numbers of eosinophils, mast cells, plasma cells, and neutrophils were found. In considering these findings, the role of chronic inflammation with T cell-dependent disturbances is discussed with regard to the pathogenesis of nasal polyps.