A number of commercial food processes involve vertical pipework, in which food mixtures are either conveyed or processed. It is important to know the flow patterns of particles within such systems. Experimental work has been carried out to study the vertical flows of solid-liquid mixtures of up to 25% solids fraction in up- and down-flow for particles of 6-10 mm diameter and for different carrier fluids: water 0.3%, 0.8% CMC and 4% starch. Particle times-of-flight were measured using metal detectors. distributions could show (i) a single peak, resulting from particle migration to particular radii, and (ii) two peaks, corresponding to wall and central regions of the flow. Data have been expressed as mean slip velocities; the greatest variation is found with starch.