This is the 31st Annual Report to Congress on the Implementation of the "Individuals with Disabilities Education Act," 2009. Section 664(d) of the "Individuals with Disabilities Education Act" ("IDEA") (P.L. 108-446), as reauthorized in 2004, requires that the Department of Education report annually on the progress made toward the provision of a free appropriate public education to all children with disabilities and the provision of early intervention services to infants and toddlers with disabilities. The report showcases the data collected from states, along with some data from a national longitudinal study that assesses the implementation of "IDEA." The report also includes information from studies, evaluations and databases of the Institute of Education Sciences and U.S. Census Bureau. This report describes our nation's progress in: (1) providing a free appropriate public education (FAPE) for all children with disabilities; (2) ensuring that the rights of children with disabilities and their parents are protected; (3) assisting states and localities in providing for the education of all children with disabilities; and (4) assessing the effectiveness of efforts to educate children with disabilities. The report focuses on the children and students with disabilities being served under "IDEA," Part C and B, nationally and at the state level. This report contains six major sections that address the five annual report requirements contained in section 664(d) of "IDEA." The sections are: (1) a summary and analysis of "IDEA" section 618 data at the national level; (2) a summary and analysis of "IDEA" section 618 data at the state level; (3) a summary and analysis of the U.S. Department of Education's (Department's) findings and determinations regarding the extent to which states are meeting the requirements of "IDEA," Parts B and C; (4) a summary of special education research conducted under Part E of the "Education Sciences Reform Act of 2002"; (5) a summary of national special education studies and evaluations conducted under sections 664(a) and (c) of "IDEA"; and (6) a summary of the extent and progress of the assessment of national activities, which focus on determining the effectiveness of "IDEA" and improving its implementation. New to the "31st Annual Report" are summaries and analyses of "IDEA" section 618 dispute resolution data. The following are appended: (1) Infants, Toddlers, Children and Students Served Under "IDEA," by Age Group and State; (2) "Developmental Delay" Data for Children Ages 3 Through 5 and Students Ages 6 Through 9 Served Under "IDEA," Part B; and (3) Differences in State Reporting of "IDEA," Part B, Disabilities.