Chapter 1 introduces the problems, confusions and issues associated with performance- and image-enhancing substances (PIEDS) use. It outlines some foundational influencers related to PIEDS use, such as their relationship to a user’s life course and the possibility that certain substances serve as gateways to others. The chapter demonstrates the need for more research examining the decision-making driving use, as well as the contextual, experiential and behavioural pathways that shape these decisions. It argues that not only must we better understand what influences decisions to employ PIEDS, but we also need to provide policy makers with solid data about how decisions may be influenced in order to produce more responsible practices in the future. Sport and health policy makers need avenues to help users mark out substance use boundaries that protect their personal health and well-being, without constraining them from improving their physical performances, and general health. We suggest that the conclusions noted in this book are important because the decision to use PIEDS can lead to serious health risks and social costs.