The paper presents experimental data on turbulent local heat transfer in a flat vertical channel with one-side heating for opposing mixed convection in wide ranges of airflow parameters (Re=4x10(3)-4x10(4); Gr(q)=1.7x10(8)-1.4x10(10); pressures p=0.2, 0.4, 0.6 MPa). Analysis has been performed by application of different buoyancy parameters. General correlation was suggested to predict the heat transfer rate. The experimental data were compared with the available correlations for vertical tubes.