Experiments are conducted to study the hydrodynamic behavior of three-phase pulp slurry systems at consistencies ranging from 0.1 to 1.0% (weight percent pulp). The pulp phase is a low-density fibrous material which swells to several times its original volume in water. The overall hydrodynamic behavior, including the regime transitions, of a multi-bubble, three-phase pulp slung is studied by measuring the overall gas holdup and by using a light transmittance probe to determine the bubble characteristics. The results demonstrate that the hydrodynamic behavior of a three-phase pulp slurry varies from the behavior of a gas-liquid system. The deviation in the behavior becomes more pronounced as the pulp consistency increases. The bubble characteristics of bubbles injected through a single bubble injector are studied in a small rectangular column through the use of now visualization and a particle image velocimetry technique. The measured change in the behavior of single bubbles injected into the pulp slurry through a single injector, is the basis for a proposed mechanism for the increased bubble coalescence in a multi-bubble system.