NCSALL's (National Center for the Study of Adult Learning and Literacy's) Adult Reading Components Study (ARCS), conducted by John Strucker and Rosalind Davidson at the Harvard Graduate School of Education, was designed to describe the various types or clusters of readers enrolled in U.S. adult basic education (ABE) programs, including both native speakers and those in English for speakers of other languages (ESOL) classes. The goal of the study was to help practitioners and policymakers understand who adult learners are as readers and how to gear instruction to their specific reading needs. (Contains 1 table.)