Numerical simulations have been conducted to study the influence of thermocapillary forces on the natural convection of a Newtonian fluid contained in an open cavity. The heated molecules of the fluid are allowed to enter the cavity region to cause the convection flow. The top horizontal surface of the cavity is assumed to be flat and free. The non dimensional partial differential equations that govern the flow and thermal fields are solved using alternate direct implicit (ADI) method together with successive over relaxation (SOR) scheme. The simulation results show that the active spot of maximum entropy generation depends on the magnitudes of Grashof number and Prandtl number, respectively. Entropy generation rate increases with the increase in the Marangoni number. The entropy generation number increases from 1 to 1.5 in the range 0 <= Ma <= 175 for Ec = 10(-4), Gr = 2 x 10(3), Pr = 0.054. The Eckert number is considered in the range of 0 <= Ec <= 0.0002. (C) 2011 Elsevier Ltd. All rights reserved.