IntroductionOver the last decade, great attention has been paid to the inclusion of newly developed nanomaterials such as nanowires, nanotubes, and nanocrystals in sensor devices. This can be attributed to the ability to tailor the size and structure, and hence the properties of nanomaterials, thus opening up excellent prospects for designing novel sensing systems and enhancing the performance of bioanalytical assays [1] . Considering that most biological systems, including viruses, membranes, and protein complexes, are naturally nanostructured materials and that molecular interactions take place on a nanometer scale, nanomaterials are intuitive candidates for integration into biomedical and bioanalytical devices [2, 3] . Moreover, they can pave the way for the miniaturization of sensors and devices with nanometer dimensions (nanosensors and nanobiosensors) in order to obtain better sensitivity, specifi city, and faster rates of recognition compared to current solutions.The chemical, electronic, and optical properties of nanomaterials generally depend on both their dimensions and their morphology [4] . A wide variety of nanostructures have been reported in the literature for interesting analytical applications. Among these, organic and inorganic nanotubes, nanoparticles, and metal oxide nanowires have provided promising building blocks for the realization of nanoscale electrochemical biosensors due to their biocompatibility and technologically important combination of properties, such as high surface area, good electrical properties, and chemical stability. Moreover, the integration of nanomaterials in electrochemical devices offers the possibility of realizing portable, easy -to -use, and inexpensive sensors, due to the ease of miniaturization of both the material and the transduction system. Over the last decade, this fi eld has been extensively investigated and a huge number of papers have been published. This chapter principally summarizes progress made in the last few years (2005 to date) in the integration of nanomaterials such as carbon nanotubes (CNTs), nanoparticles, and polymer nanostructures in electrochemical biosensing systems.