Local turbulent mixed convection heat transfer in inclined flat channels (phi = 20-90degrees from horizontal position) for opposing flows was investigated for the case when only upper wall is heated (under stably stratified flow conditions). Wide ranges of airflow parameters are covered: Re = 4 x 10(3)-4 x 10(4), Gr(q) = 1.7 x 10(8)-1.4 x 10(10), pressures; p = 0.2; 0.4; 0.6; 0.8 MPa. Based on analysis of local heat transfer data and existing information in the literature three characteristic regions in the buoyancy parameter range investigated were identified: region without buoyancy instabilities, transition region and region with buoyancy instabilities in whole heated section. For the region without buoyancy instabilities correlation for calculation of heat transfer in inclined flat channels was suggested. (C) 2003 Elsevier Ltd. All rights reserved.