The three-component flow field and spatial phase distribution of binary mixtures of glass particles suspended in water in a stirred vessel have been resolved using positron emission particle tracking (PEPT). The Lagrangian flow data provided by the technique have been converted to give a detailed Eulerian description of each of the three phase components of the flow generated by a pitched blade turbine. For the first time, it has been possible to determine the full 3D velocity and concentration fields of the liquid phase and both the solid components within opaque dense slurries of this type containing up to 40 wt % solids. Spatial distributions of local time-averaged slip velocity have also been obtained for each solid component showing wide variations. The detailed PEPT measurements have enabled the solids mass balance and the mass continuity of the three phase components to be accurately verified throughout the vessel. (C) 2010 American Institute of Chemical Engineers AlChE J, 57: 2302-2315, 2011