The rapid progress in the field of organic conducting materials has found possible applications for sensors and molecular electronics. Among them both conducting polymers and carbon nanotubes, specifically Single Walled Carbon Nanotubes and Multi Walled Carbon Nanotubes, are good candidates for these applications. Their associations can lead to the synthesis of materials called nanocomposites which resemble the whole physical and chemical properties of the starting ones. This book is therefore focused on the fabrication of nanocomposites materials, based on polyaniline derivatives and multi-walled carbon nanotubes, by means of standardized oxidative polymerization, and the subsequent characterizations by different techniques to asses the physical and chemical properties of the synthesised materials.