In this work, a numerical analysis of laminar natural convection in an enclosure of isosceles triangular cross-section has been performed for cold base and hot inclined walls. Base angles varying from 15 degrees to 75 degrees have been used for different Rayleigh numbers ranging from 10(3) to 10(5). Effects of Rayleigh number and aspect ratio on the flow field and heat transfer are analyzed. The streamline patterns and temperature distributions are presented. It is observed that the enclosures with a low aspect ratio have higher heat transfer rates from the bottom surface of the triangular enclosure. (C) 2008 Elsevier Ltd. All rights reserved.