Little research has precisely defined the population of students participating in alternate assessments based on alternate academic achievement standards (AA-AAAS). Therefore, the purpose of this article is twofold: (a) explicate the findings of a multistate study examining the characteristics of the population of students participating in AA-AAAS, and (b) discuss the implications of those findings for instruction and assessment that move us closer to understanding what these students know and can do. The article discusses the results of our study within and across these seven states, implications for practitioners, and future research directions that should be considered for both instruction and assessment. (Contains 8 tables.)