Public security and law enforcement have a crucial but often largely unacknowledged role in protecting and promoting public health. Although the security sector is a key partner in many specific public health programmes, its identity as an important part of the public health endeavour is rarely recognised. This absence of recognition has resulted in a generally inadequate approach to research and investigation of ways in which law enforcement, especially police at both operational and strategic levels, can be effectively engaged to actively promote and protect public health as part of a broader multisectoral public health effort. However, the challenge remains to engage police to consider their role as one that serves a public health function. The challenge consists of overcoming the continuous and competitive demand for police to do so-called policing, rather than serve a broader public health functionï¿½often derogatively referred to as social work. This Series paper explores the intersect between law enforcement and public health at the global and local levels and argues that public health is an integral aspect of public safety and security. Recognition of this role of public health is the first step towards encouraging a joined-up approach to dealing with entrenched social, security, and health issues.