A numerical study of the thermal stratification in an open cavity with one heated discharge is carried out. The inflow by a slot is located at the top of one vertical wall of the cavity and outflow occurs at the opposite wall. The two-dimensional flow is described by the Navier-Stokes and the energy equations. A finite difference scheme is used to solve these partial differential equations. The influence of non-dimensional parameters (Reynolds, Peclet and Richardson numbers) on the flow behavior and the stratification is examined.