This chapter presents modeled forms of the Reynolds stress and scalar flux transport equations. It is shown that the modeling of several terms of the exact Reynolds stress and scalar flux transport equation is far more complex than that of the turbulence kinetic energy equation. As a result the Reynolds stress and scalar flux transport models do not always produce more accurate results compared to the two-equation models. Finally the advantages and disadvantages of such models are compared with those of the two-equation models by means of examples from the literature.