Airways of Na+-K+-2Cl−(NKCC1)-deficient mice (−/−) were studied in Ussing chambers to determine the role of the basolateral NKCC1 in transepithelial anion secretion. The basal short-circuit current ( I sc) of tracheae and bronchi from adult mice did not differ between NKCC1−/− and normal mice, whereas NKCC1−/− tracheae from neonatal mice exhibited a significantly reduced basal I sc. In normal mouse tracheae, sensitivity to the NKCC1 inhibitor bumetanide correlated inversely with the age of the mouse. In contrast, tracheae from NKCC1−/− mice at all ages were insensitive to bumetanide. The anion secretory response to forskolin did not differ between normal and NKCC1−/− tissues. However, when larger anion secretory responses were induced with UTP, airways from the NKCC1−/− mice exhibited an attenuated response. Ion substitution and drug treatment protocols suggested that HCO[Formula: see text]secretion compensated for reduced Cl− secretion in NKCC1−/− airway epithelia. The absence of spontaneous airway disease or pathology in airways from the NKCC1−/− mice suggests that the NKCC1 mutant mice are able to compensate adequately for absence of the NKCC1 protein.