This article reviews the intended uses of these college- and career-readiness assessments with the goal of articulating an appropriate validity argument to support such uses. These assessments differ fundamentally from today's state assessments employed for state accountability. Current assessments are used to determine if students have mastered the knowledge and skills articulated in state standards; content standards, performance levels, and student impact often differ across states. College- and career-readiness assessments will be used to determine if students are prepared to succeed in postsecondary education. Do students have a high probability of academic success in college or career-training programs? As with admissions, placement, and selection tests, the primary interpretations that will be made from test scores concern future performance. Statistical evidence between test scores and performance in postsecondary education will become an important form of evidence. A validation argument should first define the construct (college and career readiness) and then define appropriate criterion measures. This article reviews alternative definitions and measures of college and career readiness and contrasts traditional standard-setting methods with empirically based approaches to support a validation argument.