Immunohistochemical stainings were performed on biopsy specimens of the middle and inferior turbinates of the nasal mucosa of 14 patients with nasal polyps and 16 healthy subjects. Significantly more CD8+ (T suppressor/cytotoxic) cells than CD4+ (T helper/inducer) cells were found in the lamina propria of the middle and inferior turbinates of patients with nasal polyps and in the inferior turbinate of healthy subjects. The middle and inferior turbinates of healthy subjects contained significantly more CD4+ cells than the middle and inferior turbinates of patients with nasal polyps. CD19+ B cells were hardly detected in the patients and healthy subjects. More HLA-DR+ cells were found in the middle than in the inferior turbinate, especially in the patients. Varying but small numbers of eosinophils, neutrophils, mast cells, and plasma cells were found in patients and healthy subjects. The possible role of CD4+, CD8+, and HLA-DR+ cells in the nasal mucosa is discussed with regard to the pathogenesis of nasal polyps.