The concept of “programme fidelity” refers to the extent that a programme is delivered as planned by programme developers (Caroll et al., 2007). Reaching a high level of fidelity has emerged as an important area of research focus for evidence-based interventions like Housing First (HF) because of its demonstrated relationship to programme outcomes such as achieving housing stability and improvements in quality of life (Davidson et al., 2014; Gilmer et al., 2015; Goering et al., 2016). A challenge associated with the international dissemination of HF (e.g., in Europe) is how the approach is adapted to different populations and policy milieus without compromising its effectiveness.

In the context of this growing diffusion of HF across North America and Europe, the purpose of this special issue of the European Journal of Homelessness is to present findings from a multi-country study of fidelity of HF programmes located in 9 countries. In conducting the research on fidelity, participating programmes followed a common research protocol that included conducting a self-assessment of programme fidelity. This was followed by qualitative interviews with programme managers and staff, intended to identify factors facilitating high programme fidelity and factors contributing to areas of low fidelity.