The European Commission's Joint Research Centre (JRC) provides scientific support to European Union (EU) policy regarding nanotechnology. Within this context, the European Commission?s Joint Research Centre launched, in February 2011, a repository for Representative Test Materials (RTMs), based on preparatory work started in 2008. The repository supports both EU and international research projects, and especially the OECD Working Party on Manufactured Nanomaterials (WPMN). The WPMN leads an exploratory testing programme "Testing a Representative set of Manufactured Nanomaterials" for the development and collection of data on characterisation, toxicological and ecotoxicological properties, as well as risk assessment and safety evaluation of nanomaterials. One important purpose is to understand the applicability of the OECD Test Guidelines for the testing of nanomaterials as well as end-points relevant for such materials. The Repository responds to a nanosafety research need which is the availability of nanomaterial from a single production batch to enhance the comparability of results between different research laboratories and projects. The availability of representative nanomaterials to the international scientific community enhances and enables development of safe materials and products. The present report describes the characterisation of Representative Test Materials of manufactured nano cerium dioxide, NM-211 and NM-212, and the bulk NM-213, each originating from a single batch of commercially manufactured material. The studies were performed in close collaboration between the PROSPEcT consortium partners, the JRC, the Fraunhofer Institute for Molecular and Applied Ecology (Fh-IME, Germany), LGC standards (United Kingdom), the National Research Centre for the Working Environment (NRCWE, Denmark), Commonwealth Scientific and Industrial Research Organisation (CSIRO, Australia) and the National Measurement Institute of Australia.