Turbulent unstratified natural convection in a vertical slot geometry is computed by integrating the unsteady three-dimensional Navier-Stokes equations. In the simulations no turbulence model is required and all the essential scales of turbulent motion are resolved. A large multiprocessor distributed memory computer is used, with satisfactory parallel efficiency, to simulate problems with up to 5 million grid points. Steady statistics are computed for Grashof numbers of 64800 and 180000. The corresponding Nusselt numbers computed for the two cases are 2.22 and 3.36. Turbulence statistics are computed for each case.