In this chapter, we consider stability, performance analysis, and control of linear (probably, uncertain) discrete-time systems. Some of the presented ideas may also be useful in the nonlinear case. Differently from continuous-time TDSs, the discrete-time ones can be reduced to non-delay systems by state/input/output augmentation. However, such an augmentation may lead to complicated systems if the delay is uncertain, variable or not small. Therefore, also in the discrete-time case, Lyapunov–Krasovskii and Lyapunov–Razumikhin methods and the small gain theorem approach lead to efficient conditions for analysis and control.