The synthesis of highly conducting polyacetylene in the late seventies inaugurated an era of extensive studies of electronic structure and transport in organic polymers. The recent attainment of conductivities in metallic polyacetylene comparable to that of copper is the outcome of major advances in the theoretical understanding and chemical synthesis of these materials. In parallel to this quest for understanding of the electronic properties of "one-dimensional" organic polymers, there has also been an active search for applications of these materials. A few applications are now reaching extensive use, among which should be mentioned polymer secondary batteries exploiting polymer materials as electrodes. Many new techniques for preparing the conductive polymers in forms suited for practical application have been proposed. For application as conductive coatings, anti- static surface treatments and electromagnetic shielding, practical use can be foreseen in the near future. One of the applications that has received considerable study, electrochromic devices utilizing electroactive polymers as active materials, has not reached that stage of maturity yet. In this short review, we present the basic physics of electrochromism in electroactive polymers, also named conductive polymers; point out the requirements for use of electroactive polymers in electrochromic devices (which includes displays, smart windows and electrooptical modulators); and describe some of the materials and processing aspects that are of particular relevance with reference to thin film technology.