On November 8-9, 2007, a meeting entitled "Setting a Public Health Research Agenda for Down Syndrome" was held to review current knowledge, identify gaps, and develop priorities for future public health research related to Down syndrome. Participants included experts in clinical and molecular genetics, pediatrics, cardiology, psychiatry, psychology, neuroscience, epidemiology, and public health. Participants were asked to identify key public health research questions and discuss potential strategies that could be used to address those questions. The following were identified as priority areas for future public health research: identification of risk and preventive factors for physical health and cognitive outcomes, focusing on understanding the reasons for previously recognized disparities; improved understanding of comorbid conditions, including their prevalence, clinical variability, natural history, and optimal methods for their evaluation and treatment; better characterization of the natural history of cognition, language, and behavior; identification of mental health comorbidities and of risk and protective factors for their development; identification of strategies to improve enrollment in research studies; development of strategies for conveying up-to-date information to parents and health professionals; identification of interventions to improve cognition, language, mental health, and behavior; understanding the impact of educational and social services and supports; identification of improved methods for diagnosis of and interventions for Alzheimer disease; and understanding the effects of different types of health care on outcomes. Participants strongly supported the development of population-based resources for research studies and resources useful for longitudinal studies. This agenda will be used to guide future public health research on Down syndrome.