The purpose of this study was to identify Cl- channels in the basolateral membrane of airway epithelial cells at the molecular level. We have focused on a new family of Cl- channels, bestrophins, which have previously been identified in retinal pigment epithelium. RT-PCR, Western blot and confocal microscopy studies revealed the presence of bestrophin in airway epithelial cells. Decreasing bestrophin expression using siRNA resulted in diminished 36Cl- flux. These studies also showed that bestrophin regulation is similar to that of native basolateral Cl- channels. The data indicate that the presence of a functional bestrophin may contribute to the basolateral cell conductance in airway epithelial cells.