Aim To evaluate the cost-effectiveness of needle and syringe programmes (NSPs) compared to no NSPs on hepatitis C virus (HCV) transmission in the United Kingdom.Design Cost-effectiveness analysis from NHS/ health-provider perspective, utilising a dynamic transmission model of HCV infection and disease progression, calibrated using city-specific surveillance and survey data, and primary data collection on NSP costs. The effectiveness of NSPs preventing HCV acquisition was based on empirical evidence.Setting UK settings with different chronic HCV prevalence among people who inject drugs (PWID): Dundee (26%), Walsall (18%), and Bristol (45%)Population PWIDInterventions Current NSP provision is compared to a counterfactual scenario where NSPs a...