Red blood cells (RBCs) or erythrocytes are the major component of blood, performing a number of essential functions. In flow, RBCs exhibit a complex dynamics which is not only fascinating scientifically but also relevant physiologically and pathologically. The effort to understand RBC dynamics in flow is a prime example of a highly fruitful interplay between different disciplines and also between experiments and computer simulations. In this chapter, the focus is on the computational models of RBCs, which represent them as two-dimensional surfaces with selected mechanical properties. The chapter starts with a description of the relevant computational models that are validated by experimental measurements of RBC mechanical properties. To illustrate the potential of these models, several numerical investigations are presented, including changes in RBC shapes, nonequilibrium fluctuations of the RBC membrane, and the behavior of RBCs in flow. These examples show that existing RBC models are quite mature and provide an important contribution to the understanding of RBC behavior in different flow environments.