The short and long forms of the D2 dopamine receptor have been expressed at similar levels in fibroblast Ltk- cells, and the long form of the receptor has also been expressed in Chinese hamster ovary cells. The ligand binding properties of the two forms of receptor expressed in different systems have been compared in saturation analyses with [3H]spiperone and in competition studies with a range of antagonists. The long form of the receptor expressed in two different cell hosts exhibits essentially identical properties. However, whereas the long and short forms of the receptor show very similar affinities for several compounds representative of different chemical classes, the short form shows a two- to fivefold higher affinity for several substituted benzamide drugs. The conformation of the receptor binding site may therefore be different in the two receptor isoforms.