The dramatic rise in intravenous drug use particularly heroin has been associated with elevated HIV transmission risk in sub-Saharan Africa. Medically Assisted Therapy is the use of prescription medical agonist to reduce the spread of HIV and viral hepatitis. The Kenyan government implemented the first MAT program in Nairobi to help address the high HIV prevalence rates (18%) and high hepatitis C prevalence rates (29%) among people who inject drugs. By 2016, only 1% of PWID were under MAT. The first research African study that was carried in the biggest drug using den in Nairobi to determine the attitude and factor associated with uptake of MAT among people who inject heroin (PWIH) and associated factors to assist in informing policy. The book details important findings that can inform policy and strengthen health systems targeting people who inject drugs.