Bubble characteristics and pressure fluctuations have been investigated in a pressurized bubble column (0.1-0.6 MPa). The bubble properties have been measured by means of resistivity probe method and the pressure fluctuations by a semi-conductor type pressure transducer. The effects of gas velocity and pressure on the bubble properties such as chord length, frequency and rising velocity have been determined. The number density distributions of the individual bubble chord length have been represented by the logarithmic normal distributions, by which the mean chord length of a bubble has been determined. The pressure fluctuations due to the bubbling phenomena in the column have been analyzed by resorting to the deterministic chaos theory; the mutual information function, phase-space portraits and correlation dimension have been obtained from the time series of pressure fluctuations. It has been found that the mutual information function, phase-space portraits and correlation dimension can be utilized to describe and explain the non-linear dynamical behaviors of gas-liquid flow as well as the bubble properties in pressurized bubble columns. They can provide quantitative measures of dynamical behavior arising from the complex gas-liquid flow. The bubble properties have been well correlated with the complex bubbling phenomena by means of the correlation dimension. (C) 1999 Elsevier Science Ltd. All rights reserved.