Abstract: This application discloses seven newly synthesized pentapeptide amides and our tetrapeptide amides. The synthesis utilized both naturally occurring and modified amino acids; the modified amino acids are constituents of the well known dolastatin 10 and dolastatin 15 which are structurally distinct peptides with excellent antineoplastic activity. These peptides were constructed by introducing a peptide bond between selected amino acids and modified amino acids and coupling the resulting di- and tri-peptides to obtain peptides having a high anticancer activity against a series of human cancer cell lines.