The "District of Columbia School Choice Incentive Act of 2003," passed by the Congress in January 2004, established the first federally funded, private school voucher program in the United States. The purpose of the new scholarship program was to provide low-income residents, particularly those whose children attend schools in need of improvement or corrective action under the "Elementary and Secondary Education Act," with "expanded opportunities to attend higher performing schools in the District of Columbia" (Sec. 303). As part of this legislation, the Congress mandated a rigorous evaluation of the impacts of the Program, now called the "DC Opportunity Scholarship Program" (OSP). This report presents findings from the evaluation on the impacts two years after families who applied were given the option to move from a public school to a participating private school of their choice. The report studies five key outcomes of the OSP: school differences; academic achievement; parental perceptions of school satisfaction and safety; student reports of school satisfaction and safety; and the impact of using a scholarship. The study found no significant differences in student achievement between those who were offered scholarships to attend a participating private school and those who were eligible for, but were not offered (as assigned by a lottery) a scholarship. However, being offered a scholarship may have improved reading test scores among three subgroups of relatively more advantaged students: those who had not attended a School in Need of Improvement (SINI) school when they applied to the program, those who had relatively higher pre-program academic performance, and those who applied in the first year of program implementation. Students in the program did not report being more satisfied or feeling safer than those who were not in the program. However, the program did have a positive impact on parent satisfaction and perceptions of school safety. This same pattern of findings holds when the analysis is conducted to determine the impact of using a scholarship rather than being offered a scholarship and when estimating the effects of attending private school versus public school, regardless of whether an Opportunity Scholarship Program scholarship was used. The following are appended: (1) Research Methodology; (2) Benjamini-Hochberg Adjustments for Multiple Comparisons; (3) Sensitivity Testing; (4) Detailed ITT Tables; (5) Relationship between Attending a Private School and Key Outcomes; and (6) Intermediate Outcome Measures. (Contains 79 tables and 11 figures.) [For the Executive Summary, see ED501697.