It is now over 30 years since the idea of ion-conducting pores burst on the elec- trophysiological scene, 15 years since these were generalIy realized to be mem- brane-spanning proteins, and 10 years since the first observations of single ion channels from higher organisms were made. During the past 5 years, several integral membrane channel proteins have been purified in a functionalIy competent state: the nicotinic acetylcholine receptor, the Na + channel, mitochondrial "VDAC," and a variety of porins. The stage is thus set to attack ion channels in the same ways that biochemists have been attacking enzymes for decades: isolation folIowed by functional analysis in as simple a system as possible, with a view towards understanding the molecular mechanisms ofthe protein's behavior and how this is related to the underlying molecular structure. This is always a daunting task, alI the more so with ion channels because of our still primitive and scanty understanding of channel structures and because of the difficulty in iso- lating functionally active channel proteins. In this volume, which can be considered a biochemically slanted companion to Sakmann and Neher's Single-Channel Recording, I have tried to present a view of the current landscape of ion-channel reconstitution. These chapters illustrate not only the different approaches and techniques of the major practitioners of ion- channel reconstitution but, as importantly, the varied motivations for doing this kind of work.