The effect of pressure on basic hydrodynamics of ebullated beds at elevated pressures of up to 15 Mpa was studied by measurement of bed profiles by gamma-ray densitometry. For 1.7 mm glass beads the bed expansion as well as gas holdup increased with pressure, while liquid and solids holdup decreased. Given the solids holdup is available, it was found that the generalized bubble wake model could be applied to compute the liquid and gas holdups of ebullated beds at high pressures. The mean absolute error of the calculated liquid holdups for the present work and for literature data was of the order of 5%. (C) 2004 Elsevier B.V. All rights reserved.