Abstract: Experiments were carried out in cylindrical Plexiglass tanks of 0.8m and 1.6m diameter agitated by single down pumping propeller (CBY).A new type of bi-electrode probe was used to measure local,three-dimensional liquid velocities in the solid-liquid system with solid volumetric concentration ( C _v) from 5.4% to 19.8%.The effects of solid volumetric concentration and scaling-up on liquid velocity distribution were studied.The down-flow outside a propeller was accelerated and the up-flow near the wall of tank was resisted by particles.The resultant liquid velocities just above the bottom of the tank are also resisted by particles.Outside the agitator radius (2 r/T>D/T ) the mean resultant liquid velocity along radius in jet region ( h/T =0.3) increases about 12% in the small tank and by 45% in the large one with solid volumetric concentration ( C _v) of 5.4%.The flow numbers were calculated for a homogeneous fluid and a suspension in the two stirred tanks.