The past decade has seen great strides in our understanding of the structure and function of protein channels that embed in lipid bilayers to allow the passage of ions a key component in many critical physiological functions, including energy and signal transduction. The determination of the crystal structures of several ion channels, as well as advances in cryo-microscopy, NMR and other spectroscopic techniques, have provided insights into mechanisms of their motions and function, including ion permeation kinetics and channel gating in response to channel-specific stimuli. The 2009 Telluride Ion Channel Biophysics Workshop (the 4th incarnation of this biennial Telluride workshop) will bring together experts in both experimental and theoretical/computational aspects of ion channel science to explore the current state of the art. In addition to fundamental molecular biophysics issues, potential ion channel based applications to biotechnology, e.g., single-molecule sensing, will also be discussed.