The cystic fibrosis transmembrane conductance regulator(CFTR) functions to regulate both CI⁻ and Na⁺ conductive pathways; however, the cellular mechanisms whereby CFTR acts as a conductance regulator are unknown. CFTR and outwardly rectifying Cl⁻ channels (ORCCs) are distinct channels but are linked functionally via an unknown regulatory mechanism. We present results from whole-cell and single-channel patch-clamp recordings, short-circuit current recordings, and [γ-³²P]ATP release assays of normal, CF, and wild-type or mutant CFTR-transfected CF airway cultured epithelial cells wherein CFTR regulates ORCCs by triggering the transport of the potent agonist, ATP, out of the cell. Once released, ATP stimulates ORCCs through a P_2U purinergic receptor-dependent signaling mechanism. Our results suggest that CFTR functions to regulate other Cl⁻ secretory pathways in addition to itself conducting C⁻.