Samples of Non Small Cell Lung Cancer (NSCLC) and normal bronchial tissue obtained in patients submitted to radical surgery and without previous exposure to cytotoxic drugs were investigated for the expression of P-170 glycoprotein using C-219 monoclonal antibody and an immunohistochemistry technique. In normal bronchial tissue the immunostaining was confined to the lumenal surface of the epithelium. Fifteen out of 86 NSCLC had more than 1/4 of examined cells positive for P-170 glycoprotein, but the heterogeneity of the expression ranged from rare scattered cells to a positive pattern for nearly all cells considered, without any relationship with pathologic and clinical prognostic variables.