The constant 1-MPa pressure filtration characteristics of a flocculated polydisperse phosphate slime slurry were examined in relation to the hydrodynamic conditions of the material's conditioning and its granulometric and textural properties. The dynamic character of the flocculation was studied by laser diffractometry. The aggregation, fragmentation and erosion of the flocs were well differentiated. The effect on the specific filtration resistance of the velocity gradient, size distribution, and porosity of the flocs was defined. With shearing at 120-2050 s(-1), the inter-floc porosity increases with decreasing granulometric spreading and increasing intra-floc porosity. A fairly high inter-floc porosity inevitably results in an increased permeability. The best filtration performances were obtained after a conditioning favouring the formation of a small distribution spreading index of floc size distribution and a high porosity cake. (c) 2008 Elsevier B.V. All rights reserved.