This working paper summarizes the results of an expert panel review of the Lexile Framework (LF). The review was conducted by five panel members through readings, the preparation of brief individual reports, and participation in a meeting held on April 26, 2001 in Washington, D.C. The list of panel members and invited observers, along with brief biographical statements, is contained in Attachment 1. The Lexile Framework is a linguistic-theory-based method for measuring the reading difficulty of prose text. Information about the Framework can be found in a number of published documents, and at the website (http://www.lexile.com). The panel's charge was to provide NCES with informed judgment on the theoretical underpinnings and construct validity of the Framework. Specifically, panel members were asked to address the Lexile Framework's basis in linguistic theory. The following questions framed the panel's work and deliberations: (1) Are word frequency and sentence length solid criteria to use in determining text difficulty?; (2) Are these criteria sufficient to determine text difficulty? If not, can they be improved or used for only a subset of reading passages?; (3) Are the procedures used to determine word frequency and sentence length, and their calibration through Rasch analysis, adequate? If not, how can they be improved? Are there alternative procedures for assessing readability?; and (4) What is the relationship between the Lexile Framework and other measures of text difficulty? In conclusion, the panel affirmed the value of both sentence length and word frequency as overall measures of semantic and syntactic complexity (although participants diverged on whether these constructs were best viewed as proxies or as direct measures). The following attachments are included: (1) Lexile Framework Assessment Panel Members and Invited Observers; (2) Invited Papers: Adams, M. J.; Kamil, M.; Larson, R.; Smith, C.; and Wrigley, H. S.; and (3) Comments from Lexile Framework Developers.