Background and Aims: Globally, the morbidity and mortality attributable to hepatitis C virus (HCV) infection is increasing. The nature and magnitude of the hepatitis C epidemic is poorly described in most countries, including Norway. Reliable epidemiological data are essential when planning health programs for treatment and prevention, especially targeting persons who inject drugs (PWID) who are most at risk of becoming infected and infecting others. The main aim of this ongoing study is to assess the prevalence of HCV in high-risk populations. Methods: In this study, we implemented mobile, on-site HCV screening to reach at-risk populations in Trondheim, Norway. Inclusion started in September 2015. Two dedicated study nurses frequently visited the local opioid substitution clinic, outpatient clinics and day centres for PWID, as well as the local prison and refugee healthcare centre. Demographic data, risk behavior and clinical symptoms were obtained by a study questionnaire. Subjects with a positive anti-HCV rapid test were subsequently tested for serum HCV RNA and the virus genotyped. Subjects with detectable HCV RNA were offered transient liver elastography using a mobile FibroScan402 unit. Results: Recruitment of PWID was time-consuming. Word-of-mouth within the targeted population seemed to impact recruitment. By November 2016, 304 people had been tested. 148 (41%) had a positive HCV rapid test result, and of these, 90 (73%) were also HCV RNA positive. 102 had been injecting drugs for over 10 years, 4 were cirrhotic (≥12.5 kPa or higher). HCV genotypes 1a (29%) and 3 (59%) were most prevalent. Of 25 subjects previously treated, 8 had detectable HCV RNA (32%), 3 of these were likely reinfected. None of the 52 immigrants were HCV positive. 32 of the 62 subjects included while in prison had a history of intravenous drug use, and HCV prevalence was similar to PWID outside of prison. All except one person wished to be evaluated for treatment, however, many failed to keep follow-up appointments. Conclusions: PWID have a high prevalence of HCV, but only 17% of HCV positive PWID had previously been treated. 22 study participants should have been considered for treatment according to current national guidelines, but most had not sought help in the local health care system. This study demonstrates that establishing an outreach system for HCV screening among PWID in a defined geographical area is feasible and should be considered to increase treatment uptake among at-risk populations.