A new method of scaling three-phase fluidized beds is presented based upon achieving geometric and dynamic similitude with the aid of the Buckingham Pi theorem. This results in five dimensionless groups that must be matched to ensure hydrodynamic similarity between separate units. Experiments have been carried out to validate this technique by comparing gas hold-up and bed expansion in two different columns operating with significantly different fluid and solids properties, but where efforts have been made to match the five dimensionless groups. These comparisons show mostly favourable agreement between the two units.