Abstract: Radial profiles of local gas and solid holdups and liquid interstitial velocity were measured in a largediameter three-phase fluidized bed, and a systematic study was carried out in comparing the present data with those obtained in small-diameter beds. Radial profiles of local gas holdup were found to be parabolic; the distribution of local solid particle holdup could be expressed by Eq. (9); liquid interstitial velocity was well described by the modified circulating flow model.