Sets of dimensionless groups from the literature used for scaling are classified according to the number of groups in a set. At least five dimensionless groups are required for full hydrodynamic scaling of a Circulating Fluidised Bed (CFB). Sets of four groups, given by Glicksman, Hyre and Woloshun (1993, Powder Technology, 77, 177-199) and Horio, Ishii, Kobukai and Yamanishi (1989, Journal of Chemical Engineering of Japan, 22(6), 587-592) and sets of three groups given by Glicksman (1988, Chemical Engineering Science, 43, 1419-1421) and Horio et al. (1989) are in both cases shown to give essentially equivalent scaling. A survey concludes that most experimental results reported in the literature scale up better to catalytic cracking CFBs than to CFB combustors.