Environmental and economic considerations require that tailings disposal systems are performed using much higher solids content than was previously deemed acceptable. These new high concentration systems have many benefits, particularly lower water consumption, smaller impoundment areas and reduced solids' mobility. These systems require that the solids are pumped out to the deposition sites as non-Newtonian suspensions which are generically,. although nearly always erroneously, called pastes. This paper will present results gathered in recent years which demonstrate that such suspensions are almost invariably stratified, especially if the suspension's size distribution is wide, a prerequisite for co-disposal systems. it will also show that the transport pressure gradients are substantially different from those predicted from simplistic paste theory for full size plant. These findings will be supported by experimental observations using both visual, MRI and ERT tomography data and from mathematical modelling results. (C) 2005 Elsevier Ltd. All rights reserved.