A numerical study has been carried out for the two-dimensional laminar natural convection in a pitched roof of triangular cross-section under summer day boundary conditions. Stream function-vorticity formulation was applied and control volume integration solution technique is adopted in this study. Solutions are obtained up to Rayleigh number of 10(6). Steady-state solutions have been obtained for height-base ratios of 0.125 less than or equal to L*less than or equal to 1. The effects of height-base ratio and Rayleigh number on the flow structure and heat transfer are investigated. It has been found that a considerable proportion of the heat transfer across the base wall of the region takes place near the intersection of the cold horizontal wall and hot inclined wall. The relationship between the mean Nusselt number, Nub, the Rayleigh number, Ra, and the height-base ratio, L*, is such that for equivalent changes in Rayleigh number and height-base ratio, the influence of height-base ratio is the considerable higher factor. Comparisons with earlier works were also made. (C) 2000 Elsevier Science S.A. All rights reserved.