Reduction in energy requirement for hydraulic transportation of solids has been the main concern of researchers. Investigators have reported considerable reduction of head loss in rectangular ducts than traditional circular pipes. In the present study, concentration profiles for six particle sizes ranging from 38 to 739 pm were measured using a traversing mechanism and isokinetic sampling probe at nine levels in the vertical plane for multisized particulate zinc tailings slurry flowing through rectangular duct having hydraulic diameter of 80 mm, width of 200 mm and height of 50 mm. The experiments were conducted at different flow velocities ranging from 1 to 4 m/s using five efflux concentrations ranging from 4% to 26% by volume for each velocity. Solids concentration profiles were found to be a function of particle size, velocity of flow and efflux concentration of slurry. Solids concentration varied with the vertical position, except for particle size of 38 mum. Experimental data for pressure drop were also collected at six efflux concentrations ranging from 0% to 26% at flow velocities ranging from 1.0 to 4 m/s for each efflux concentration. Pressure drops and solids concentration profiles data measured in the present study for rectangular duct are compared with previous data for 105 mm diameter pipe. (C) 2003 Elsevier Ltd. All rights reserved.