The 5' untranslated leader sequence from the encephalomyocarditis virus was used to engineer bicistronic or tricistronic expression vectors encoding two subunits (P2X2 and P2X3) of an ATP-gated cation channel. Human embryonic kidney (293) and chinese hamster ovary (CHO-K1) cells were transfected with the vector, and stable cell lines were generated by single cell subcloning. Selection was made in a 96-well format on the basis of a sustained increase in intracellular calcium (fluorescence of Fluo3-loaded cells) evoked by the ATP analog alpha beta methylene ATP. A high proportion of transformants expressed heteromeric receptors containing both P2X2 and P2X3 subunits, as evidenced by a nondesensitizing current in response to alpha beta methylene ATP. The method is fast and simple and could be generally useful for the stable expression of heteromultimeric channel proteins.