Results obtained recently demonstrate that many organic molecules can be designed to provide nonlinear susceptibilities far larger than those of lithium niobate. These molecules may be attached to polymer chains to create films of large area with good mechanical properties as well as the required optical performance. Applications that have been predicted include second-harmonic generation, optical modulation, optical switching, and memories. For these hopes to reach fruition, highly ordered polymer films incorporating these molecules must be fabricated. Among the most promising techniques being pursued is Langmuir-Blodgett deposition, in which monolayers can be extracted from a water subphase onto a substrate. The interleaving of film materials permits the creation of multiple-layer systems between 5 A and 5000 A thick. In this paper we review both the research directed toward molecular design and the efforts to grow multilayer crystalline polymer films.