Trends in educational research, teaching practices, and teacher responsibilities change over time. There is currently a movement away from relying on summative assessment and large-group research to assessing individual students on a formative basis. This push is partially legal, and the 2004 Individuals with Disabilities Education Improvement Act (IDEIA) is encouraging adoption of Response to Intervention (RtI) at all levels of education. One research methodology that is particularly poised to meet the call by IDEIA is single-subject research designs, which have recently been endorsed by the What Works Clearinghouse. This article provides an overview of common single-subject designs, discusses the underlying logic of these designs, identifies many advantages this methodology provides to the classroom, and describes the dimension of behavior that may be measured and graphed for visual analysis. Understanding single-subject research designs and their use at the middle and secondary level is one of the first steps toward implementation of the RtI model after elementary school. (Contains 6 figures.)