Global health and environmental issues, such as the HIV/AIDS epidemic, or global climate change, are increasingly perceived as security issues by policymakers, members of the civil society or the private sector, and populations at large. This working paper seeks to elucidate the very process through which this situation came to be - the securitization process of health and environmental issues - through a historical contextualisation of the process, and a description and analysis of its development. This paper is also intended to provide the departure point for the 'Health and Environment: from Security and Safety Issues to New Governance Options' programme of the Ifri. By providing theoretical and analytical tools, a historical perspective and a robust methodology, this paper sets the stage for the study of the impacts of the securitization of health and environmental issues on the governance options available to actors, and on the efficiency of solutions.