Multiple radioactive particle tracking is a noninvasive technique used to study flow phenomena within gas-solid fluidized beds. Five tagged polyethylene particles were added to a fluidized bed and tracked using two gamma cameras set perpendicular to one another. One camera collected x-z particle locations and the other collected y-z particle locations, while both cameras collected particle count rate values. The x-z and y-z particle movement information was combined to form three-dimensional particle trajectories, and in turn used to calculate instantaneous flow information. The information from the five particles was then averaged and used to calculate three-dimensional information regarding solid circulation parameters.