The author has proposed a new theory of suicidal behavior--the interpersonal-psychological theory of suicidal behavior (Joiner, 2005)--which attempts to answer the question "Why do people die by suicide?" In this commentary, he briefly describes the theory, and then argues that the theory's constructs may allow a new level of focus and specificity for suicide prevention in general and for school-based suicide prevention in particular. In so doing, he discusses his colleagues' findings and concepts from this special series and suggests some avenues for future research.