The steady two-dimensional viscous supersonic turbulent flow over a backward facing step was calculated using the PHOENICS CFD code. The two-equation k{ turbulence model was employed for the turbulent  flow simulation. The effects of the incoming boundary layer, Reynolds number and inlet Mach number on the flow were investigated. The maximum free stream Mach number was 3.5. The PHOENICS code was found to be adequate for supersonic flow simulations with M63:5, however, at hypersonic turbulent flow conditions convergence was not obtained. The numerical results indicate that the separation point is positioned on the step face, below the corner. The calculations also show that a lip shock is formed to match the flow conditions at the step corner. The results exhibit favorable agreement with data from both experiments and other numerical simulations.