With reading, as with all academic content and skills, effective instruction is informed by sound assessment. Teachers' knowledge about classroom-embedded reading assessment must continue to be developed so that they can use the information it yields to make informed instructional decisions. At the same time, districts and schools must develop systematic, coherent, and reliable assessment programs that ensure consistency within and across grades while complementing and building on informal assessment efforts already underway. This Knowledge Brief explains the importance of early assessment and identifies some of its basic purposes; describes the challenges of assessing young children; explains some basic approaches to literacy assessment and how they align to specific purposes; and identifies some of the issues that need to be addressed if schools are to undertake valid and reliable literacy assessment whose results can help teachers better support all young readers. The brief is intended to help district administrators, principals, and other instructional leaders begin laying the groundwork for more consistent and effective use of reading assessment in the early primary grades. It is also intended to help them better understand the nuances and limitations of various instruments, including what decisions they can support. (Contains 2 figures, 25 endnotes, and 29 references.) (NKA)