Postsecondary readiness enables students to pursue their dreams, contribute to society, and thrive in the global economy. Since many accountability systems include a postsecondary readiness indicator in formal evaluations of schools and districts, it benefits educators, families, researchers, policymakers, and other education partners to understand how postsecondary readiness is defined, measured, and used. This brief, produced by the Region 15 Comprehensive Center, explains how states define and measure postsecondary readiness, an important step toward improving how such measures function within state accountability systems. Region 15 Comprehensive Center staff identified four main findings about the use of postsecondary readiness indicators, the types of measures included in the indicators, and how much weight indicators are given in accountability systems: (1) More than three of four ESSA plans contained a postsecondary readiness indicator; (2) States included three main types of measures in postsecondary readiness indicators: academic, career, and military; (3) Postsecondary readiness indicators focused most heavily on academic and career measures and less on military measures; and (4) Weighting of the postsecondary readiness indicator varies widely from state to state.