Speech and language are central to the human experience; they are the vital means by which people convey and receive knowledge, thoughts, feelings, and other internal experiences. Acquisition of communication skills begins early in childhood and is foundational to the ability to gain access to culturally transmitted knowledge, organize and share thoughts and feelings, and participate in social interactions and relationships. Thus, speech disorders and language disorders--disruptions in communication development--can have wide-ranging and adverse impacts on the ability to communicate and also to acquire new knowledge and fully participate in society. Severe disruptions in speech or language acquisition have both direct and indirect consequences for child and adolescent development, not only in communication, but also in associated abilities such as reading and academic achievement that depend on speech and language skills. The Supplemental Security Income (SSI) program for children provides financial assistance to children from low-income, resource-limited families who are determined to have conditions that meet the disability standard required under law. Between 2000 and 2010, there was an unprecedented rise in the number of applications and the number of children found to meet the disability criteria. The factors that contribute to these changes are a primary focus of this report. "Speech and Language Disorders in Children" provides an overview of the current status of the diagnosis and treatment of speech and language disorders and levels of impairment in the U.S. population under age 18. This study identifies past and current trends in the prevalence and persistence of speech disorders and language disorders for the general U.S. population under age 18 and compares those trends to trends in the SSI childhood disability population. (Individual chapters contain references.) The following are appended: (1) Glossary of Key Terms; (2) Descriptions of Data Sources; (3) Population and Administrative/Service Data for Speech and Language Disorders; (4) Description of Methods Used to Calculate Trends in National Survey Data; (5) Review of Social Security Administration Case Files; (6) Workshop Agendas; (7) Summary of "Mental Disorders and Disabilities Among Low-Income Children"; and (8) Committee member Biographies. [The content of this document was prepared by the Committee on the Evaluation of the Supplemental Security Income (SSI) Disability Program for Children with Speech Disorders and Language Disorders; Board on the Health of Select Populations; Board on Children, Youth, and Families; Institute of Medicine; Division of Behavioral and Social Sciences and Education; National Academies of Sciences, Engineering, and Medicine.]