This paper introduces a general overview of polymer- and biopolymer-clay nanocomposites showing attractive properties for electrochemical and electroanalytical applications, including the latest advances achieved in this field by our research group. A part of the paper is devoted to introducing the many advances carried out since our pioneering work on PEO-smectite nanocomposites, including new approaches of synthesis and processing to improve the performance of these systems as solid electrolytes. Nanocomposites involving conducting polymers, e.g., polyaniline (PANI) and polypyrrole (PPy), as well as precursors of conducting materials, e.g., polyacrylonitrile (PAN), are currently tested as active phases of electrodes for different electrochemical devices. The combination of clays and biopolymers produces bio-nanocomposites that can be used as active phase of electrochemical sensors for the detection of ionic species. (c) 2005 Elsevier B.V. All rights reserved.