Natural convection of air in a two-dimensional, rectangular enclosure with localized heating from below and symmetrical cooling from the sides has been numerically investigated. Localized heating is simulated by a centrally located heat source on the bottom wall, and four different values of the dimensionless heat source length, 1/5, 2/5, 3/5 and 4/5 are considered. Solutions are obtained for Rayleigh number values from 10(3) to 10(6). Local results are presented in the form of streamline and isotherm plots as well as the variation of local Nusselt number on the heated wall. Finally, the average Nusselt number at the heated part of the lower wall, was shown to increase with an increase the Rayleigh number. Ra, or of the,nondimensional heat source thickness, epsilon.