The network-on-chip paradigm is an emerging paradigm that effectively addresses and presumably can overcome the many on-chip interconnection and communication challenges that already exist in today's chips or will likely occur in future chips. Effective on-chip implementation of network-based interconnect paradigms requires developing and deploying a whole new set of infrastructure IPs and supporting tools and methodologies. This special issue illustrates how, to date, engineers have successfully deployed NoCs to meet certain very-aggressive specifications. At the same time, the articles reveal many issues and challenges that require solutions if the NoC paradigm will indeed become a panacea or quasi-panacea for tomorrow’s SoCs.