The research on students who do not graduate from high school has traditionally focused on students who drop out before their expected graduation date. This ignores the experiences of "persisters" or "persisting students"--those who remain enrolled in high school on or beyond their expected graduation date, but have yet to earn a diploma. Where data are available persisting students are estimated to be equal to or greater in number than dropouts. Authors argue that persisting students warrant greater attention in research, policy, and practice efforts meant to better understand and promote high school completion and the postsecondary transition. To this end, this article summarizes the existing literature on persisting students, with attention to how they are defined, their sociodemographic and academic characteristics, and the schools they attend. The article also lays out a research agenda and policy implications, highlighting the importance of better understanding this group and meeting their needs more effectively with the twin goals of (1) adding nuance to our understanding of persisting students and (2) improving the precision in educational research more broadly.