While products based on nanotechnology are actually reaching the market, sufficient knowledge on the associated toxicological risks is still lacking. Reducing the size of structures to nanolevel results in distinctly different properties. As well as the chemical composition, which largely dictates the intrinsic toxic properties, very small size appears to be a predominant indicator for toxic effects of particles. Based on these conclusions, the development of specific guidance documents at a European level for the safety evaluation of nanotechnology products applied in medical technology is strongly recommended and the need for further research in the field of nanotoxicology is clearly identified.For medical applications, immobilized nanostructures inside or on surfaces of medical devices such as surgical implants are expected to pose a minimal risk as long as they remain fixed. Release due to continuous chemical processes and/or mechanical stress at the interface of implants and surrounding tissues might yield potential risks, however. For medical applications utilising free nanoparticles or nanostructures, for example novel drug delivery systems, the specific toxicological properties have to be investigated. It is insufficient to rely on knowledge of the classical toxicity testing of chemical(s) and materials when the risks of nanoparticles and/or nanostructures have to be assessed. From a regulatory point of view, a risk management strategy is already a requirement for all medical technology applications. With regard to applications utilizing nanotechnology this is considered sufficient, as long as manufacturers, notified bodies and competent authorities are made aware of the need to carry out a dedicated (nano)toxicological risk assessment.