This report summarises the discussions of a workshop on the development of a categorisation approach for manufactured nanomaterials in order to improve the decision making process. The end goal was to agree on a set of recommendations on how to move forward so manufactured nanomaterials could be categorised for each focus area for testing, for read across/structure-activity relationships (SARs), for use in hazard assessment and exposure and risk assessment, and to better target risk management. The categorisation scheme would take into consideration the chemical composition and shape and properties such as surface charge of the chemicals. A categorisation scheme needs to be able to be used within a regulatory scheme.