In this paper, the flow of a powder through a silo is investigated using Digital Speckle Radiography (DSR). This technique allows displacement measurements to be made on the sub-mm scale to an accuracy of 0.06 mum and a spatial resolution of 26 mum. The method performs an image cross-correlation on a random seeding of X-ray opaque material as it flows out of the silo with the powder. The flow is captured digitally using a continuous X-ray source and an image intensifier and Charge Coupled Device (CCD) camera to give real time measurements. The powder used is Al2O3 with an average particle size of 50 mum and the seeding material is tungsten powder, also with an average particle size of 50 mum. Clear flow behaviour is observed for two different sizes of outlet and the flow rate and strains occurring during the flow are also investigated. (C) 2004 Published by Elsevier B.V.