The ACM Symposium on Spatial User Interaction (SUI) is the first international symposium focused on the user interface challenges that appear when users interact in the space where the flat, two-dimensional, digital world meets the volumetric, physical, three-dimensional (3D) space we live in. This considers both spatial input and 3D output, with an emphasis on the issues around interaction between humans and systems. Due to the advances in 3D technologies, spatial interaction is now more relevant than ever. Powerful graphics engines and high-resolution screens are now ubiquitous in everyday devices, such as tablets and mobile phones. Moreover, new forms of input, such as multi-touch, finger and body tracking technologies are now easily available. In this environment, spatial UIs are transitioning out of the research community and game industry. More and more commercial 3D systems with spatial interaction capabilities exist, many priced at the consumer level. Until now, the challenges, limitations, and advantages of using this third dimension for human-computer interfaces have not been well understood. These questions will only become more relevant as the associated technologies continue to cross the barrier towards wide adoption. The goal of the symposium is to provide an intensive exchange between industrial and academic researchers working in the area of spatial user interaction and to foster discussions among participants. ACM’s Special Interest Groups on Graphics and Computer-Human Interaction (SIGGRAPH and SIGCHI) co-sponsor the event. The two-day symposium will be held in 2013 in conjunction with ACM SIGGRAPH 2013, and will take place prior the ACM SIGGRAPH 2013 conference. In 2014, the event is planned to take place in conjunction with UIST 2014.