Preliminary identification of C-terminus of trichosanthin by chemical and enzymic methods,such as hydrazinolysis,thiohydantoin reaction and carboxypeptidase hydrolysis,showed that theremay be the possible presence of more than one terminus,i.e.,Met and Ala but complicated by sidereactions.A computer-assisted carboxypeptidase method was first introduced by the authors to de-termine the C-terminal sequence of trichosanthin,and showed that trichosanthin is heterogeneous at itsC-terminus and has two C-terminal sequences determined as-Arg-Asn-Asn-Met-OH and-Arg-Asn-Asn-Met-Ala-OH respectively.These results have been later unambiguously confirmed by the re-sults from other experiments through the identification of the free alanine always present in the CNBr de-gradation products of trichosanthin,and the actual separation of two fragments from the finger printsas well as from the HPLC fractions of the trypsin digest of this protein.All shows that their aminoacid sequences,determined by manual DABITC/PITC technique,agree well with those of the twoC-terminal seauences determined by the computer-carboxypeptidase method. Preliminary identification of C-terminus of trichosanthin by chemical and enzymic methods, such as hydrazinolysis, thiohydantoin reaction and carboxypeptidase hydrolysis, showed that there is the possible presence of more than one terminus, ie, Met and Ala but complicated by sidereactions. A computer- assisted carboxypeptidase method was first introduced by the authors to de-termine the C-terminal sequence of trichosanthin, and showed that trichosanthin is heterogeneous at its C-terminus and has two C-terminal sequences determined as-Arg-Asn-Asn-Met-OH and-Arg-Asn-Asn-Met-Ala-OH respectively.These results have been omitted unambiguously confirmed by the re-sults from other experiments through the identification of the free alanine always present in the CNBr de-gradation products of trichosanthin, and the actual separation of two fragments from the finger prints as well from from HPLC fractions of the trypsin digest of this protein. All shows that their aminoacid sequences, determined by manual DABITC / PITC technique, agree well with those of the two C-terminal selections determined by the computer-carboxypeptidase method.