This chapter is to outline the design, synthesis, chemical and functional characterization of a set of structurally related branched polymeric polypeptides with poly[Lys] backbone. It has been documented that the composition and amino acid sequence of the branch could markedly determine the physico-chemical characteristics including solution conformation, the interaction phospholipid mono- or bilayers as well as the biological properties, like cytotoxicity, blood clearance, biodistribution, immunoreactivity of the compound and even related bioconjugates with chemotherapeutic agent, peptide epitope or reporter entity. The synthesis, structural and functional characterization of conjugates, in which (i) various antitumour, antiparasitic compounds (e.g. daunomycin, methotrexate, GnRH analogue), (ii) imaging agents (e.g. radionuclides, fluorophores) or (iii) B- and/or T-cell epitope peptides from viral (e.g. Herpes simplex virus), bacterial (e.g. M. tuberculosis) and various disease (e.g. tumour, Alzheimer disease) related proteins are attached covalently to selected poly[Lys] branched polymeric polypeptides are discussed.