In October 2003, the US Department of Education contracted with Abt Associates to design and conduct the Reading First Implementation Evaluation. This report focuses on the following questions: (1) How is the Reading First program implemented in districts and schools? and (2) How does reading instruction differ in Reading First schools and non-grantee Title I schools The Reading First program's overarching goal is to improve the quality of reading instruction--and thereby improve the reading skills and achievement of children in the primary grades--by providing substantial resources at both the state and local levels. The five-year study has produced this interim report based on data collected during the 2004-05 school year as well as analyses of extant data sources. The following are appended: (1) The Study Samples and the Sampling Weights; (2) Survey Instruments; (3) Back-up Exhibits; and (4) The Construct Matrix. (Contains 61 exhibits and 52 footnotes.) [This report was prepared with assistance from: Robert St. Pierre; Beth Gamse; Alan Werner; and Quentin Dixon.]