Laminar and turbulent natural convection in enclosures with partial partitions has been studied by a numerical method. Vertical boundaries were isothermal and horizontal boundaries were adiabatic. Two dimensional equations of conservation of mass, momentum and energy, with the Boussinesq approximation are solved using the Simpler method. Various geometrical parameters were: aspect ratio A=0.3 to 0.4, partition position D=0.5-0.6, height of the partitions C=D=O to 0.15. The Rayleigh number was varied from 10(4) to 10(11). The results are reduced in terms of the normalized Nusselt number as a function of the Rayleigh number, and other non dimensional geometrical parameters. The isotherms and streamlines are produced for various Rayleigh numbers and geometrical conditions. Heat transfer correlations useful for practical design problems have been derived.