On further study of the computer-assisted carboxypeptidase method for sequencing the C-terminals of proteins or peptides,two computer programs-DPS and CPA were successfully developedon VAX-11/780 computer and tested with some synthetic peptides and the degradation fragment ofthe natural protein as model substrates.The C-terminal sequence of CB-3,one of the CNBr degra-dation fragments of trichosanthin,had first been determined by this method as:-Ser-Ala-Ser-Ala-Ala-Leu-Hse-OH,which was later confirmed by other ways of sequencing.This method is not only ableto extend the C-terminal sequencing up to 7 amino acid residues,but also useful for determining theC-terminal sequence with repeating amino acid residues.