Transmembrane ion channels regulate the movement of ions (particularly Na+, K+, Ca2+ and Cl-) across cellular membranes, and are critical to numerous aspects of neurobiology. Cells express a diverse array of ion-channel proteins that vary widely in their ion selectivity and in their modulation by ligands (such as neurotransmitters) or by membrane voltage. Most ion channels are multisubunit proteins and, as such, undergo an intricate series of post-translational folding, modification and oligomerization events to achieve their correct functional quaternary structure. The means by which the cell is able to accomplish this complex process of ion-channel assembly is a topic that is beginning to be addressed experimentally.