Minimum pick-up velocities (U-pu) for entrainments of particle mixtures having binary particle size distributions (PSD) are measured in a horizontal pneumatic-conveying line using the weight-loss method. Geldart's groups A, B, and C glass beads having diameters of 400, 170, 40, and 5 pm are used. Variations in U-pu as a function of particle mass fraction (m) are examined. The capability of empirical correlations of monodisperse U-pu in predicting U-pu of binary mixtures is investigated. For group B particle mixtures (i.e. 400 & 170 mu m), the particles are entrained separately resulting in linear U-pu variations with m, which is accurately predicted by the monodisperse U-pu correlation. For mixtures involving group A and B particles (i.e. 170 & 40, 400 & 40 mu m), the two particles are collectively entrained resulting in U-pu that vary non-linearly with m and that cannot be predicted by the correlation. For mixtures involving group B and C particles (i.e. 400 & 5, 170 & 5 mu m), U-pu are comparable to that of the monodisperse group B particles, therefore they are accurately predicted by the correlation. The significant impacts of binary PSD on U-pu found presently indicates that PSD effects on particle entrainment process warrants further investigations. (C) 2010 Elsevier B.V. All rights reserved.