Clinical research involving children with hypertension poses unique opportunities and challenges. In particular, the complications of hypertension accrue over the course of many years and are relatively infrequent, so studies need to be large and long term to identify clinically important end points. Despite the challenges, an evidence base is beginning to amass that should eventually answer many of the relevant questions. We now have a good idea of how blood pressure tracks from the beginnings of life to early adulthood and an understanding of the relative importance of different risk factors. This chapter aims to inform the reader of different study designs as they apply to pediatric hypertension, and how these can be applied to answer specific questions of clinical importance. We also discuss the strengths and weaknesses of different study designs, and the results of some particularly impactful trials are discussed. Recent advances in study design and epidemiology are covered, with a focus on the potential role of data sharing.