Background. In July 2012 the Research and Training Center on Community Living at the University of Minnesota hosted a State-of-theScience Conference on Community Living Outcomes and Quality of Life (SOSC). The purpose of this conference was to bring together researchers and other stakeholders to provide a summary of what is known, identify points of debate and gaps, and establish recommendations for future research related to community living outcomes and quality of life in for people with intellectual and developmental disabilities (IDD). The conference had a number of focus areas, including: social inclusion; self-determination; family experiences, support and siblings; employment; health and wellness; methodological issues in research; quality of life indicators; outcome predictors; and using outcome data to inform policy. The State of the Science Conference was a vehicle through which these key topics related to community living and participation could be discussed and future research goals identified. This special issue of Intellectual and Developmental Disabilities (IDD) includes papers written by the presenters and participants of the SOSC on key topics associated with community living outcomes. The purpose of this introduction is to place the special issue papers in a broader research, policy and service-delivery context. The phrase ‘‘state-of-thescience’’ connotes rigorous, technical analysis of scientific knowledge using techniques such as systematic reviews and meta-analysis. These are valid approaches, but they require a level of research evidence and a consistency in outcomes measures that are rarely available in IDD research. As Moseley, Kleinert, Sheppard-Jones, and Hall (2013, this issue) note, public policy draws on the best available evidence, and often cannot wait for gold-standard randomized control design studies to be completed. Moreover, in many public policy areas, including IDD services, it is neither possible, nor ethical, to randomly assign people with IDD to treatment and non-treatment groups. Nature of the special issue papers. Instead of systematic reviews, this special issue presents a series of expert commentaries and narrative reviews that focus on important policy-related and conceptual issues that were examined at the State-of-theScience Conference. As Lakin (2012) noted, ‘‘In policy research it is often necessary to accept the preponderance of good evidence through comprehensive reviews of all the available credible evidence’’. Ideally, such reviews select the best available evidence and analyze and interpret it in a manner underpinned by a detailed understanding of the circumstances in which the evidence was obtained, and of the IDD policy and service-delivery context in which the conclusions are to be applied. We hope readers will find that the commentaries, reviews and analyses presented in this special issue display these characteristics. US focus drawing on US data. One feature of a number of the special-issue papers is a strong focus on outcomes, services, policy and research involving people with IDD in the US. A related characteristic is that many of these papers draw on data from one or more US national surveys, such as the Administration on Intellectual and Developmental Disabilities (AIDD) Projects of National Significance. These projects include the National Core Indicators project (Human Services Research Institute and the National Association of State Directors of Developmental Disability Services), Residential Information Systems Project (University of Minnesota), State of the States in Developmental Disabilities Project (University of Colorado, Boulder) and Access to Integrated Employment: National Data Collection on Day and Employment Services for Citizens with Developmental Disabilities (University of Massachusetts, Boston). However, the spotlight on the US is not all encompassing. For example, Amado, Stancliffe, McCarron and McCallion (2013, this issue) draw on national findings from Ireland arising from the Intellectual Disability Supplement to The Irish Longitudinal INTELLECTUAL AND DEVELOPMENTAL DISABILITIES