This article presents a study of the fluidization of solids dispersed in size and density simultaneously. Minimum and complete fluidization velocities of these solids are measured and compared with their U(mf) distribution. Extensions of some correlations established for binary mixtures are also proposed. The axial mixing state of the beds near these two velocities is then evaluated by sampling, and expressed in terms of several indices : size index, density index and the combined U(mf) index. In contrast with U(mf), the axial profile of the bed is mainly controlled by the density distribution of the materials. An index based on the pressure drop along the bed height gives an on-line indication of that segregation.