“…In some populations, the RCT design might be difficult, untenable, or sometimes even inappropriate (Miller & Brody, ). Particularly in cases of hard‐to‐reach and vulnerable populations, such as refugee and marginalized communities (see Ponguta et al., 2019, this issue) or children and adolescents in residential care institutions (see Tavecchio et al., 2019, this issue), researchers are confronted with many practical, methodological, political, legal, and/or ethical challenges. The goal of this issue is to catalog such challenges of conducting an RCT and explore alternatives and supplementary study designs that address these challenges.…”