Preliminary studies including feasibility and pilot studies are a critical component of research. Feasibility and pilot studies can identify methodological, practical, and ethical concerns prior to an ex-pensive full-scale study. This chapter explores the differences and similarities between feasibility and pilot studies. In addition, key methodological (i.e., retention, sampling, outcome selection) and analysis considerations in preliminary research are discussed. Finally, researchers are provided with guidance for reporting standards and moving from feasibility and pilot studies to full-scale studies.