Over the past few decades, reading assessment has been pushed to the forefront of the national discussion about education. The most recent reauthorizations of the Elementary and Secondary Education Act (1994, 2001) made assessment a priority as administrators and teachers are attempting to meet increasing accountability standards, but measuring reading ability is a difficult task. The complexity of the reading process makes it challenging to assess exactly what is happening when readers read and understand text. Part of this challenge could be that research into the assessment and treatment of reading difficulties has developed a focus on maximizing intervention effects. Though ensuring that reading interventions have the strongest impact on student performance, the focus on performance has arguably migrated the field away from interventions that are based on reading theory. Both theory and student performance are important foci, but maximum effect sizes in intervention research and maximum differentiation in assessment research could drift to align more closely over time as intervention research uses the tests designed to differentiate. This could potentially narrow the functioning construct of reading in assessment and intervention to become unidimensional, which could lead to ignoring important aspects of reading that are more difficult to measure or change through intervention. The four articles included in this special series all relate to the assessment of oral reading. They illustrate some of the advances yet to be made in the field in order to continuously define "best practice." In this article, the authors provide an overview of the need for and purpose of reading assessment, summarize each of the articles in this special series, and explore the need for assessment and intervention that is aligned with specific components of reading, as well as general reading ability.