Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel cause the genetic disease cystic fibrosis (CF). The commonest CF mutation, F508del-CFTR causes a temperature-sensitive folding defect leading to three fundamental insults: (1) aberrant protein processing and trafficking; (2) defective channel gating and (3) thermal instability1. To restore CFTR function to CF patients, CFTR correctors have been developed to rescue the cell surface expression of F508del-CFTR. Here, we investigate the single-channel properties and thermostability of F508del-CFTR delivered to the cell surface by VX-809, the first CFTR corrector to be tested in the clinic2,3. In comparison, we studied F508del-CFTR rescued by low temperature-incubation. We incubated BHK cells expressing F508del-CFTR with VX-809 (3 µM) for 24 h at 37 °C prior to single-channel recording at temperatures between 23 – 37 °C using excised inside-out membrane patches. Alternatively, BHK cells were incubated at 27 °C for 24 h and studied as a control. The channel activity of F508del-CFTR rescued by either low temperature or VX-809 was much reduced compared to that of wild-type CFTR. Instead of the exponential increase in open probability (Po) observed with wild-type CFTR between 23 and 37 °C, the temperature-dependence of Po for F508del-CFTR rescued by either low temperature or VX-809 was bell-shaped with a maximum around 30 °C. For F508del-CFTR rescued by VX-809, a subtle increase of the maximal Po was observed compared to low temperature, although no statistical significance was achieved. (Control, 0.081 ± 0.016; VX-809, 0.098 ± 0.016, means ± S.E.M, n = 7 – 10, P > 0.05, student t-test). Over the temperature range 23 – 37 °C, no difference was observed between the single-channel current amplitude of wild-type CFTR and F508del-CFTR rescued by the two methods. However, at high temperatures, F508del-CFTR rescued by either low temperature or VX-809 frequently opened to sub-conductance states, which were very rarely observed with wild-type CFTR. Like low temperature-rescued F508del-CFTR, VX-809-rescued F508del-CFTR channels were unstable and ran down at 37 °C. We conclude that VX-809 restores similar temperature-dependent channel behaviour to F508del-CFTR as rescue by low temperature-incubation. This suggests that VX-809 and low temperature might share a common mechanism of rescuing the F508del-CFTR folding defect. Our observation that VX-809 delivers F508del-CFTR to the cell surface without improving its gating defect and thermal instability suggests that CF patients with the F508del-CFTR mutation will likely require combination drug therapy.