The scaling relationships proposed by Glicksman (Chem. Engng Sci. 39, 1373-1379, 1984) for fluidized-bed scale-up have been modified to provide a full set of scaling parameters for spouted bed scale-up. A force balance for particles in the annulus region of a spouted bed leads to addition of two non-dimensional parameters, the internal friction angle (phi) and the loose packed voidage (epsilon(o)) to the original Glicksman scaling relationships. Experimental verification of the full set of modified scaling parameters was conducted, first in a series of small spouted beds, then in larger columns up to 0.914m in diameter, and finally in a pair of high-temperature (500 degrees C) columns. Both viscous and inertial forces were important for the conditions investigated so that the full set of scaling parameters is tested initially. It is demonstrated that the full set of modified scaling parameters is valid for spouted beds when all dimensionless parameters are matched between the prototype bed and model beds. For example, a corresponding dead zone was observed at the bottom of the annulus not only in the 0.914 m diameter column, but also in a properly scaled 0.152 m diameter column. Reasonably, close similarity could also be achieved by substituting U/U-ms for the Reynolds number as a dimensionless group. Successful scaling could not be achieved by varying only the bed and particle dimensions. Internal angles of particle friction and sphericities significantly influence the maximum spoutable depth, fountain height and longitudinal pressure profiles, showing that particle-particle interaction forces cannot be ignored in spouted bed scale-up.