On June 12-14, 2012, the Board on Global Science and Technology held an international, multidisciplinary workshop in Washington, D.C., to explore the challenges and advances in intelligent human-machine collaboration (IH-MC), particularly as it applies to unstructured environments. This workshop convened researchers from a range of science and engineering disciplines, including robotics, human-robot and human-machine interaction, software agents and multi-agentsystems, cognitive sciences, and human-machine teamwork. Participants were drawn from research organizations in Australia, China, Germany, Israel, Italy, Japan, the Netherlands, the United Arab Emirates, the United Kingdom, and the United States. The first day of the workshop participants worked to determine how advances in IH-MC over the next two to three years could be applied solving a variety of different real-world scenarios in dynamic unstructured environments, ranging from managing a natural disaster to improving small-lot agile manufacturing. On the second day of the workshop, participants organized into small groups for a deeper exploration of research topics that had arisen, discussion of common challenges, hoped-for breakthroughs, and the national, transnational, and global context in which this research occurs. Day three of the workshop consisted of small groups focusing on longer term research deliverables, as well as identifying challenges and opportunities from different disciplinary and cultural perspectives. In addition, ten participants gave presentations on their research, ranging from human-robot communication, to disaster response robots, to human-in-the-loop control of robot systems. Intelligent Human-Machine Collaboration: Summary of a Workshop describes in detail the discussions and happenings of the three day workshop.