The multi-phase nature of granular pastes, coupled with their non-Newtonian rheology and inherent inhomogeneity, makes characterisation and prediction of flow behaviour challenging. We focus on stiff pastes which can maintain their shape after extrusion. We describe how the approach presented by Benbow and Bridgwater can be used to predict the deformation and flow behaviour of such materials. Illustrations are drawn from industrial pastes and applications studied in our group. Its basis in viscoplasticity and pure plasticity is discussed. Problems associated with stiff pastes are highlighted. Finally, a roadmap is presented summarising how we think the progress of paste understanding needs to be developed. (c) 2011 Canadian Society for Chemical Engineering