Collective Behavior is the summary of the 2014 National Academies Keck Futures Initiative Conference on Collective Behavior. Participants were divided into fourteen interdisciplinary research teams. The teams spent nine hours over two days exploring diverse challenges at the interface of science, engineering, and medicine. The composition of the teams was intentionally diverse, to encourage the generation of new approaches by combining a range of different types of contributions. The teams included researchers from science, engineering, and medicine, as well as representatives from private and public funding agencies, universities, businesses, journals, and the science media. Researchers represented a wide range of experience - from postdoc to those well established in their careers - from a variety of disciplines that included science and engineering, medicine, physics, biology, economics, and behavioral science. The teams needed to address the challenge of communicating and working together from a diversity of expertise and perspectives as they attempted to solve a complicated, interdisciplinary problem in a relatively short time. This report highlights the presentations of the event and includes the team reports and pre-meeting materials.