cDNAs complementary to pig kidney mRNAs coding for alpha- and beta-subunits of Na+,K+-ATPase were cloned and sequenced. Selective tryptic hydrolysis of the alpha-subunit within the membrane-bound enzyme and tryptic hydrolysis of the immobilized isolated beta-subunit were also performed. The mature alpha- and beta-subunits contain 1016 and 302 amino acid residues, respectively. Structural data on the peptides from extramembrane regions of the alpha-subunit and on glycopeptides of the beta-subunit underlie a model for the transmembrane arrangement of Na+,K+-ATPase polypeptide chains.