It is difficult to observe directly the particle motion inside a dense granular flow or a fluid-particle flow because of the existence of surrounding particles. MRI (Magnetic Resonance Imaging) is one of the noninvasive and non-destructive measurement techniques for such flows. MRI can measure the velocity distribution (tagging method and phase method), which is an outstanding advantage of the MRI measurement. This paper briefly explains the principle of the MRI measurement. Then MRI is applied to some dense granular flows or fluid-particle flows, such as the rotating drum, vibrated granular bed, hopper flow and spouted bed. (C) 2010 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.