Nanoparticles (NPs) have unique, potentially beneficial properties, but their possible impact on human health is still not known. The area of nanomedicine brings humans into direct contact with NPs and it is essential for both public confidence and the nanotech companies that appropriate risk assessments are undertaken in relation to health and safety. There is a pressing need to understand how engineered NPs can interact with the human body following exposure. The FP7 project NanoTEST (www.nanotest-fp7.eu) addresses these requirements in relation to the toxicological profile of NPs used in medical diagnostics.