Structural regulation and functional development of the polymeric multilayers prepared by the recently developed layer-by-layer (LbL) assembly technique are reviewed. Stereocomplexes formed between chemical-structurally regulated synthetic polymers were used in the LbL assembly, and the resulting films have potential applications in biomedical and other technological fields. The addition of inorganic salts into aqueous solutions of bioactive polyelectrolytes made it possible to fabricate the multilayers with a variable surface charge density. The bioactivities such as blood coagulation, enzymatic degradation, and cell responses were strongly dependent on the charge density as well as the outermost polymer component. Novel ultrathin films were fabricated by repetitive physical adsorption/drying processes from salt-containing aqueous solutions of strongly intra- and inter-active polymers. Furthermore, ultrathin films fabricated by chemical cross-links between polymers with a hydrophilic neutral unit caused an increaseinthe film thickness, in water, producing ultrathin hydrogels on the surfaces. These results will open a new field of polymer surface science.