The amino acid sequence of the phosphorylase kinase δ subunit has been determined using cyanogen bromide peptides. These peptides were ordered by isolation of the tryptic peptides containing carboxy[14C]methylmethionine. The protein is identical to bovine uterus calmodulin and differs from bovine brain calmodulin only in amide assignments. The δ subunit contains 148 amino acids, including one residue of trimethyllysine, and has a molecular weight of 16680. The N terminus is blocked, probably with an acetyl group, and the protein has a net overall charge at pH 7 of –24. The asparagine residues 60 and 97 have been shown to be partially deamidated in the protein. The sequence of the N-terminal tripeptide and the amide assignments on residues 58 and 60 were not determined unequivocally.