The existence of a chromosome gene family containing at least one gene and one pseudogene was shown for the Na+,K+-ATPase β-subunit. A partial structure of the βI-gene was determined, the coding part of which was completely homologous to cDNA of the Na+K+-ATPase βI-subunit from HeLa cells [8]. The region encoding the putative protein transmembrane domain was shown to be bordered by two introns. The structure of a pseudogene (βψ) was determined. This pseudogene is processed and contains multiple stop codons. Its homology to the βI-subunit cDNA from HeLa cells is about 88%. © 1989.