The N-terminal sequences of the alpha and beta subunits from the Na/K-ATPase of duck salt gland have been determined by automated Edman degradation chemistry. These sequences were compared to sequences previously reported for Na/K-ATPase subunits from other sources in order to determine the subunit isoform composition of the salt gland enzyme. The comparisons indicate that the duck salt gland enzyme is composed of an alpha-1 subunit and a beta-1 subunit. This subunit isoform composition is consistent with the involvement of this enzyme in sodium excretion as Na/K-ATPases in other tissues involved in sodium excretion also have this subunit isoform composition.