This investigation was undertaken to study the flow of vapors through moving beds of catalyst in which the entire bed moves with respect to the walls of the container, but the moving particles remain in a fixed position relative to each other.The experimental data obtained include studies on both concurrent and countercurrent flow of air through such beds. The material employed included granular, spherical, and pellet types of catalyst ranging in size from 4 to 60 mesh and representing both uniform grades and mixtures of sizes. Various spherical shaped seeds as well as 0.25and 0.375-inch alumina spheres were employed also.