New fluidization experiments have been carried out with: a binary mixture containing 2.5 and 3.5 mm particles in equal proportions, some binary mixtures containing 1.5 and 2.5 mm particles in several proportions, and a ternary mixture containing 1.5, 2.5 and 3.5 mm particles in equal proportions. The segregation behavior of the mixtures of spherical glass particles was studied in a pseudo two-dimensional laboratory scale gas-fluidized bed with the aid of a newly developed non-intrusive Digital Image Analysis technique. The segregation index introduced by Goldschmidt et al. [1] has been used to quantify the segregation dynamics in binary mixtures, and two adapted forms of it have been used to study the segregation dynamics of the ternary mixture. Furthermore, a (mean) height index was introduced to provide more details about the dynamics of the ternary system. Our experiments reveal that while the binary systems could segregate slightly at fluidization velocities exceeding the incipient velocities of the individual components, the ternary mixture becomes well mixed at velocities even well below the incipient fluidization velocity of the large, 3.5 mm particle. (C) 2013 Elsevier B.V. All rights reserved.