A recent trend in language assessment has been to assess examinees’ abilities to integrate source reading or listening material into their writing and speaking performance in ways that simulate the cognitive, communication, and literacy demands of real-life academic or vocational tasks. This chapter describes the justifications for this innovation in interactionist theories of communication, cognition, and assessment; through appeals to authenticity and relevance; and as a means to counter the effects of testing methods. The chapter explains how and why integrated skills assessment differs from the convention of assessing writing, speaking, reading, and listening as separate skills but also produces unique complications for measurement, test design, and examinee performance. Future directions are proposed to refine the constructs and tasks guiding integrated skills assessment, to increase their value for diagnostic purposes, and to verify their proposed benefits for teaching, learning, and high stakes decision making such as university admissions or employment.