Akiyama MJ, et al. - Researchers examined 2,188 participants comprising people aged 18 years or older who were living in Nairobi, coastal Kenya, or western Kenya, had a history of injection drug use, and had used any illicit drugs in the past 12 months for the prevalence of HCV mono-infection and HIV–HCV co-infection, and the estimated incidence, genotypes, and risk behaviors associated with HCV. Two hundred ninety-one of the participants (13%) were anti-HCV positive: 183 (22%) of 842 participants in coastal Kenya, 105 (13%) of 817 in Nairobi, and three (1%) of 529 in western Kenya. Among people who inject drugs in Kenya, they observed variation in HCV prevalence, estimated incidence, and risk behaviors with the region; the highest estimated incidence was observed in coastal Kenya. In the coastal region, increased risk of HCV was observed in correlation with history of incarceration, more years injecting, more injections in the past month, and receptive cooker sharing, while in Nairobi, increased risk of HCV was observed in correlation with female gender, more years injecting, more injections in the past month, and regular use of a syringe with a detachable needle. Among HIV-positive participants, HCV prevalence of 50% (66 of 131 participants) was observed in coastal Kenya, 35% (42 of 121) in Nairobi, and 4% (one of 23) in western Kenya. Risk factors for HIV–HCV co-infection and those observed for HCV mono-infection were similar. Genotypes prevalent were 1a (51%), 4a (47%), and mixed (2%; three 1a/4a and one 1a/2b). These findings may assist in informing focused strategies to decrease HCV transmission, such as augmentation of needle and syringe programs, upscaling of opioid agonist therapy, and treatment as prevention in regions afflicted by injection drug use and HCV.