This paper presents performance tests of a higher-order turbulence closure model for the predictions of turbulent shear flows. Computations of the momentum and temperature fields in the flow domain being considered entail the solutions of the Reynolds-averaged transport equations containing the second-order turbulence fluctuating products. Computations of the Reynolds stresses are performed with three closure models and the k-c model (one of the Boussinesq viscosity models). Computations of the second-order temperature velocity products are achieved by closing the pressure-heat flux term. These predictions are compared with three sets of experimental data. Several advantages have been observed in using the higher-order transport equations for evaluating Reynolds stresses; considerable improvement is achieved when higher-order turbulence closures are employed. This is because the Boussinesq viscosity model assumes that turbulence is isotropic and thus overpredicts the transverse normal component of the Reynolds stresses.