The past year has seen remarkable progress in defining the structure of various ligand-gated ion channels. Images of opened and closed nicotinic acetylcholine receptors at 9 A resolution have now made it easier to identify the conformational changes underlying gating. In addition, recent studies on glutamate receptors have led to a radical revision of their postulated transmembrane topology: models for agonist-binding and allosteric domains now use sites previously thought to lie in cytoplasmic loops. Other areas that are being actively pursued include identification of the amino acids lining the ion channels, accurate measurements of Ca2+ fluxes, and tests of transmembrane topology in kainate receptor subunits.