Abstract: Investigations of the transition from bubbling to turbulent fluidizationwere conducted in a gas-solid fluidized bed using on-line computer analysis of pressure fluctuations. In order to study the effects of density and size of the particles as well as bed geometry on the transition, a series of experiments were performed, resulting in the following conclusions. 1. The technique of pressure fluctuation analysis was found effective and reliable in fluidization studies. 2. A correlation was obtained for the effect of powder properties and fluidized bed geometry on the transition velocity, Uc from bubbling to turbulent fluidization: 3. Addition of a new Yc-axis to Geldarts classification diagram is suggested, ia order to predict such flow pattern transition.