Ligand-gated channels (LGCs) play a fundamental role in the fast transmission of electrical activity from neuron to neuron and/or to effector cells. Studies of LGCs in isolation have become possible since the identification of genes coding for these membrane proteins together with the establishment of reconstitution techniques in host systems. Methods for electrophysiological investigations of LGCs reconstituted either in the Xenopus oocytes or stably tranfected in cell lines are discussed. Functional studies of reconstituted receptors enable fast determination of LGCs' pharmacological profiles and comparison of their physiological properties. Combination of molecular engineering with physiological measurements allows studies with unpreceeding resolution and it is now possible to examine at the amino-acid level the contribution of some residues in the formation of the ligand-binding site or the ionic channel domains.