In networked control systems (NCS), one or more dynamical systems are controlled by feedback over a communication network. The transmission capacity of the communication network is limited. This limits the number of bits or packets per second which can be transported via the network and, consequently, restricts the achievable performance. This area has grown rapidly in the last few years with the emergence of applications ranging from micro-electromechanical chips and Internet congestion protocols to ``drive-by-wire" systems. Many attractive advantages of introducing a communication network, like high system testability and resource utilization, as well as low weight, space, power and wiring requirements, motivate the research on the NCS. On the other hand, networks can introduce unreliable and time-dependent levels of service in terms of delays, jitter, data packet losses, and so on. My research in this area is related to various stability analysis and controller design issues for NCS.