RTAS’15, the 21st in a series of annual conferences sponsored by the IEEE, will be held in Seattle, Washington, as part of the Cyber-Physical Systems Week (CPSWeek) in April, 2015. CPS Week 2015 will bring together leading conferences, including the International Conference on Information Processing in Sensor Networks (IPSN’15), the International Conference on Hybrid Systems (HSCC’15), the International Conference on Cyber-Physical Systems (ICCPS’15), the International Conference on High Confidence Networked Systems (HiCoNS’15) and RTAS’15. RTAS’15 invites papers describing original systems and applications, case studies, methodologies and applied algorithms that contribute to the state of practice in the broad field of embedded and open real-time systems and computing. The scope of RTAS’15 will consist of three tracks: (1) Applications, RTOSs and Run-Time Software and Tools, (2) Applied Methodologies and Foundations, and (3) Embedded Systems Design for Real-Time Applications.