A number of aspects of interfaces in polymeric materials are reviewed. The emphasis is in the relationships between the structure and the mechanical properties of the interfaces. Attention is restricted to amorphous materials but both glassy and elastomeric polymers are considered. In many cases the interface structure is controlled by placing a thin layer of a diblock copolymer at the interface. The diblock copolymer can act to increase the adhesion between the materials on both sides and so toughen the interface. Interface failure requires that the diblock copolymer molecules either break or pullout from one side or the other. The criteria for chain pullout are discussed together with the interfacial toughness obtained with both pullout and chain scission failure. For elastomeric materials pullout is considered both in the adhesion situation, where the relative deformation of the two materials is normal to the interface, and the friction situation where the deformation is in the plane of the interface.