The Fourth International Conference on NPS is supported by UNODC and organized by the University of Hertfordshire, “Sapienza” University of Rome, the University of Chieti-Pescara, EMCDDA as well as WADA. The recent emergence of NPS, combined with the ability of the Internet to disseminate information quickly, have raised a number of challenges in the fields of drug policies, substance use research and public health. Despite increasing amount of attention being given to this area, NPS are rarely mentioned in scientific literature, and there is limited information available on their nature and potential risks.  Such a phenomenon highlights the importance of multi-national and multi-disciplinary collaboration in order to enhance knowledge and improve the quality of information sharing and good practices at a global level. The main aim of the fourth edition is to increase knowledge and understanding about the nature and the effects of NPS as well as promote innovative strategies to prevent the diffusion of NPS in society.