Segregation of solid spherical particles differing both in size and in density during the rapid gravity flow of a mixture down a rough inclined chute is analysed in the present paper. The phenomenon of separation of particles having different mass under the influence of the solid phase concentration gradient is investigated experimentally and analytically. The phenomenon is analogous to that studied previously (D.J. Stephens and J. Bridgwater, Powder Technol., 21 (1978) 17-44) in experiments with an annular shear cell. The authors' general model of the segregation dynamics published earlier is further developed. The results of modelling are described and compared with the experimental data.