Experimental measurements of the average gas hold-up, a key parameter in the design and operation of three-phase (gas-liquid-solid) fluidized beds, are extracted from a multitude of published studies, classified and correlated for the first time. A simple functional, based on power-law dependence of the average gas hold-up on a number of dimensionless variables, successfully correlates gas hold-up during gas flow in fluidized beds of spherical particles with pure water as the liquid phase. Best-fit parameters of such a functional result in prediction of more than 75% of the data with absolute relative error less than 20%, but are shown to depend on the morphology of three-phase flow and may be difficult to generalize. (C) 2016 Elsevier B.V. All rights reserved.