In these 2014 consolidated guidelines on HIV prevention, diagnosis, treatment and care for key populations, the World Health Organization (WHO) brings together all existing guidance relevant to five key populations – men who have sex with men, people who inject drugs, people in prisons and other closed settings, sex workers, and transgender people – and updates selected guidance and recommendations. These guidelines aim to: provide a comprehensive package of evidence-based HIV-related recommendations for all key populations; increase awareness of the needs of and issues important to key populations; improve access, coverage and uptake of effective and acceptable services; and catalyze greater national and global commitment to adequate funding and services.