Acetylcholine receptors are cationic channels whose opening is controlled by acetylcholine. They are key molecules in the cholinergic nicotinic transmission in a number of areas of the central and peripheral nervous system. Because of the structural complexity, given by the numerous subunits that forms these receptors, they have different pharmacological and biophysical properties. Here we give a brief account of the known and consolidated data regarding neuronal nicotinic receptors, as as an introduction to the articles reported in this issue, in order to allow readers who are not familiar with the field to place the detailed information in the right context.