Synthetic biology -- unlike any research discipline that precedes it -- has the potential to bypass the less predictable process of evolution to usher in a new and dynamic way of working with living systems. Ultimately, synthetic biologists hope to design and build engineered biological systems with capabilities that do not exist in natural systems -- capabilities that may ultimately be used for applications in manufacturing, food production, and global health. Importantly, synthetic biology represents an area of science and engineering that raises technical, ethical, regulatory, security, biosafety, intellectual property, and other issues that will be resolved differently in different parts of the world. As a better understanding of the global synthetic biology landscape could lead to tremendous benefits, six academies -- the United Kingdom's Royal Society and Royal Academy of Engineering, the United States' National Academy of Sciences and National Academy of Engineering, and the Chinese Academy of Science and Chinese Academy of Engineering -- organized a series of international symposia on the scientific, technical, and policy issues associated with synthetic biology. Positioning Synthetic Biology to Meet the Challenges of the 21st Century summarizes the symposia proceedings.