This paper reports on an extensive experimental campaign aimed at studying the influence of interparticle forces on the fluidization behaviour of fine group A powders by changing the size distribution of the fine sub-cuts (particles below 45 mu m) and with increasing temperature. The fluidization behaviour of an alumina powder was investigated at temperatures ranging from ambient up to 400 degrees C and by adding to the material previously deprived of fines two fine sub-cuts of nominal size 0-25 mu m and 25-45 mu m, respectively. Four samples were investigated, containing 22% and 30% wt of fines and having similar particle size distribution but shifted towards smaller and bigger fines sub cuts. Fluidization and rheological tests were performed in parallel. Results obtained from pressure drop profiles, bed expansion profiles and bed collapse test were linked to the rheological analysis of the failure properties of the materials. The static angle of internal friction phi, the effective angle of internal friction phi(e), cohesion C, the angle of wall friction phi(w) and wall adhesion A, the dynamic angle of internal friction delta and dynamic cohesion C-delta were determined to underpin the role of the interparticle forces on the ability of the powders to flow and to their fluidization quality when adding small or big fines to the material. (c) 2006 Elsevier Ltd. All rights reserved.