The scale-up method for three-phase fluidized beds hydrodynamics proposed by Safoniuk et al. [M. Safoniuk, J.R. Grace, L. Hackman, C.A. McKnight, Chem. Eng. Sci. 54 (1999) 4961], based upon the principles of dynamic similitude, was tested matching several systems operated at high pressure with model systems operated at atmospheric pressure. Experiments were carried out to test this technique by comparing global phase holdups, and flow regime in systems where the five dimensionless groups proposed by the method were matched, but which were operated at significantly different pressures. The differences observed between the hydrodynamic parameters of the high pressure and model systems suggest that the five dimensionless groups employed are not enough to fully characterize the global bed behavior. Similar findings have been reported by Macchi et al. [A. Macchi, H. Bi, J.R. Grace, C.A. McKnight, L. Hackman, Chem. Eng. Sci. 54 (2001)] based on differences observed in the local dynamic bed behavior between systems operated at atmospheric pressure. (C) 2007 Elsevier B.V. All rights reserved.