This treatise is a compendium of papers based on invited talks presented at the American Chemical Society Symposium on Electroactive Polymers which covered nonlinear optical polymers and conducting polymers, the common denominator being the correlated pi-electron structures. The improved understanding of the consequences of pi-electron delocalization upon nonlinear optical properties and charge carrier dynamics has laid the foundation for the rapid development and application of the electroresponse of conjugated polymers. As a result, the area of electroactive and nonlinear optical polymers is emerging as a frontier of sCience and technology. It is a multidisciplinary field that is bringing together scientists and engineers of varied background to interface their expertise. The recent explosion of interest in this area stems from the prospect of utilizing nonlinear optical effects for optical switching and logic operations in optical computing, optical signal processing, optical sensing and optical fiber communications. Polymers and organic are rapidly becoming one of the major material classes for nonlinear optical applications along with multiple quantum wells, ferroelectrics and other oxides, and direct band-gap semiconductors. The reasons for this lie in the unique molecular structures of polymers and organics and the ability to molecularly engineer the architecture of these structures through chemical synthesis.