While HIV prevalence among the general population in Tanzania is 4.7 percent, the rates among key populations are much higher. HIV prevalence among people who inject drugs is 35 percent. Among men who have sex with men, the rate is 25 percent, and among female sex workers, it is 15.4 percent. High HIV prevalence among key populations is propelled by gender-based violence, stigma, and the criminalization of these groups. EpiC Tanzania provides technical assistance and service delivery among key populations, adolescent girls and young women (AGYW), and other adult men and women at higher risk.