The mouse genes for cytosolic phosphoenolpyruvate carboxykinase-1 (Pck-1) and neuronal nicotinic acetylcholine receptor alpha 4 subunit (Acra-4) both map to distal chromosome 2 (Siracusa et al. 1989; Bessis et al. 1990). We have utilized Southern blot analysis on human/rodent somatic cell hybrids to map the human homologues of both of these genes, PCK1 and CHRNA4, to human chromosome 20.