A library of nine monoclonal antibodies which bind to the alpha subunit of human erythrocyte spectrin has been established. The specificity of these antibodies confirms the alignment and uniqueness of each of the five previously identified peptide domains in this subunit and establishes the identity of additional smaller proteolytic peptide fragments. This immunochemical approach is complementary to the identification of peptide relationships by two-dimensional chymotryptic peptide mapping, and the results of both methods are in complete agreement.