In multiconstituent polymers there exists a driving force for the lowest energy constituent to preferentially adsorb at the surface, or for a surfactant-like species to preferentially reside at a polymer-polymer interphase. The occurrence of this interphase partitioning can drastically alter the surface and/or interfacial properties of multicomponent polymers, and is the basis of many commercial methods for surface property modification. This research represents a comprehensive effort to understand the fundamental principles underlying these phenomena by thorough experimentation on several model systems. These include miscible homopolymer blends, immiscible ternary homopolymer/homopolymer/block copolymes blends, functionally terminated homopolymers, and immiscible blends of functionally terminated homopolymer with a second homopolymer. Characterization of the surface tension, and surface chemical structure and composition is accomplished by application of a number of current surface and interface analysis techniques in order to relate these features to the bulk physical and thermodynamic parameters of the constituents. The availability of this information will assist in the molecular design of surface and interfacial modifiers for multiconstituent polymers.