Screen-printing technology is a standard method used in electronics that has been applied to produce low-cost disposable electrochemical biosensors. The procedure consists in deposition of successive layers of conducting pastes onto a solid support. These pastes are composed of graphite or metallic nanoparticles, a polymeric binder and additives, and have well-defined physical properties (viscosity, drying, curing temperature, screen properties, storage). Typically, the last layer is used to cover the working electrode surface onto which the biological recognition element is attached. Therefore, its formulation strongly affects the performance of the biosensor device. Depending on the requirements of a specific application and the biological reagent used, this ink can contain functional materials such as conducting polymers, cofactors, stabilizers and mediators, and more recently metal nanoparticles and carbon nanotubes. This presentation will focus on the nanomaterials used to fabricate screen-printed biosensors and their impact on the overall performance of these devices. We will describe several strategies for the incorporation of biomolecules onto screen-printed electrodes and their applications for toxicity monitoring. Issues of biocompatibity will also be discussed.