In this chapter, we will give an overview of the methods for making electrical recordings from single ion channels in cell membranes and in planar lipid bilayers, endeavoring to point out the advantages and limitations of each approach. Since extensive treatments of various aspects of the techniques are currently available, including complete books devoted to patch clamping (Sakmann and Neher, 1983a ) and to ion channel reconstitution (Miller, 1986 ), we attempt to present an integrated view, with references to other discussions of details of the theory and practice that provide additional information that might be necessary to establish these techniques in the laboratory. Since the techniques of single-channel recording are being applied to an expanding range of biological problems, numerous companies are beginning to address the needs of researchers in these areas. Consequently, we will list some sources of useful equipment, software, and supplies. Finally, we will attempt to highlight current developments in instrumentation and techniques, which have appeared since other reviews were written. Of particular interest are recent approaches to presentation, analysis, and modeling of single-channel data that have just appeared or are in press at the time of writing of this article.