This article examines three typical approaches to alternate assessment for students with significant cognitive disabilities--portfolios, performance assessments, and rating scales. A detailed analysis of common and unique design features of these approaches is provided, including features of each approach that influence the psychometric quality of their results. Validity imperatives for alternate assessments are reviewed, and approaches for addressing the need for validity evidence are outlined. The article concludes with an examination of three technical challenges--alignment, scores and scoring, and standard setting--common to all alternate assessments. In light of these challenges, existing methods and professional testing standards are endorsed as necessary guidance for understanding and advancing alternate assessment practices.