Although changes of cohesive behaviour of powders is observed at high temperature in several industrial process units, conventional testers and procedures are still not suited for testing powder flow properties at high temperature. In this work a High Temperature Annular Shear Cell was designed, built and set-up in order to directly measure the flow properties of powders up to 500 degrees C. A temperature control system was also developed to establish a uniform temperature inside the powder sample. Yield loci at room temperature and 500 degrees C were measured for samples of fluid catalytic cracking catalyst (FCC powder), fly ashes, natural corundum, synthetic porous alpha-alumina and glass beads. Experimental evidences did not reveal a univocal effect of temperature in the tested range. Finally, shear tests on glass beads mixed to with some high-density polyethylene (HDPE) (1% of the total weight) confirmed that a significant increase of the cohesive behaviour occurs at high temperature when liquid bridges form due to the melting of one of the solid phases. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.