A CYCLIC AMP-stimulated choride conductance appears when the cystic fibres is gene is expressed in non-epithelial cells by infection with recombinant viruses^1,2. Cyclic AMP-stimulated conductance in this system is mediated by the same ohmic, low-conductance Cl^- channel as in human secretory epithelia^2–4, but control of this channel by phosphorylation has not been directly demonstrated. Here we report the appearance of the low-conductance Cl^- channel in Chinese hamster ovary cells after stable transfection with the cystic fibres is gene. The channel is regulated on-cell by membrane-permeant analogues of cAMP and off-cell by protein kinases A and C and by alkaline phosphatase. These results are further evidence that the cystic fibrosis transmembrane regulator is a Cl^- channel which can be activated by specific phosphorylation events and inactivated by dephosphorylation; they reveal an unsuspected synergism between converging kinase regulatory pathways.