The "First-Year Effects of Early Indicator and Intervention Systems in Oregon" study provides information to the Oregon Department of Education and Oregon districts that are adopting or considering adopting an early indicator and intervention system (EIIS), as well as to other interested state and district education leaders who are considering a similar system. This appendix provides an overview of the literature on EIISs, including key indicators of high school dropout and graduation; which grade levels to focus on, as identified in the research for preventing high school dropout; and the evidence on EIISs that was available before this study. It then summarizes the history of Oregon Ballot Measure 98 and the High School Success Initiative during its first two years to provide additional context. Finally, it offers a more detailed description of each component of an EIIS. [For the full report, see ED614630. For the Study Snapshot, see ED614631.]