Natural convective motion within a three-dimensional rectangular enclosure is numerically simulated using a time-split finite-element method. Differential heating from either the side or bottom surface is examined for Rayleigh numbers of 104and 105with a Prandtl number of 1.0. The time-dependent primitive equations of motion are solved using a form of the SIMPLE algorithm. Linear basis functions are used with a dissipation parameter based on a Petrov-Galerkin procedure. A simple tridiagonal solver is used to obtain the solution to the matrix set of equations. Three-dimensional stereographic images of the results are displayed.