Effects of pressure on the bubble properties, such as pierced length, rising velocity, and frequency, and on the minimum fluidization velocity were determined in gas-solid fluidized beds by means of a cross- correlation function and a power spectrum of pressure fluctuations. The pressure fluctuations along the axial distance above the distributor were measured by a differential pressure transducer in the pressurized gas-solid fluidized bed [0.1 m (I.D.) 2.0 m (high)] Sand and silica sand, having mean diameters of 0.59 and 0.18 mm, respectively, and each having an apparent density of 2590 ㎏/㎥, were used as bed materials. The pierced length and rising velocity of the bubbles decreased, but the bubble frequency increased, upon an increase in the system pressure. The minimum fluidization velocity of the particles decreased considerably upon increasing the system pressure. The bubble flow behavior in the bed became more periodic and predictable as the bed pressure increased.