Abstract A non-intrusive measurement technique has been developed for accurate determination of gas and particle velocities in a turbulent two-phase flow field. The principle of the technique is based on the discrimination between the scattered light from particles and the fluorescence emission from particles coated with a fluorescent dye. A high-powered, argon-ion based, single-channel, on-axis backscatter laser-Doppler velocimetry system was used. The fluorescent dye was Rhodamine 6G. A study of the gas-solid two-phase flow behaviour in the freeboard of a cold gas-fluidized bed was undertaken. The solid phase contained two particle groups: bed material (sand) and fuel particles (wood). Measurements of the axial velocity and turbulence intensity distributions of the gas phase and both particle groups within the solid phase were made along the column centre and across the freeboard. Excellent discrimination of velocities from the two phases and from the two particle groups within the solid phase was achieved.