The Linkages across the Continuum of HIV Services for Key Populations Affected by HIV (LINKAGES) project conducts a range of HIV prevention activities to reduce HIV transmission among key populations (sex workers, men who have sex with men, transgender persons and people who inject drugs) and to improve their enrollment and retention in care. These briefs offer up-to-date knowledge and tools from LINKAGES country programs that can be used to strengthen HIV and AIDS programming for key populations worldwide.