The Kolmogorov entropy (KE) algorithm was applied successfully to gas holdup fluctuations measured in a 0.102 m I.D. stainless steel bubble column equipped with a perforated plate distributor (19 holes 0 1 mm). Nitrogen was used as the gas, while both I-butanol and gasoline were used as liquids. I-Butanol was aerated at pressures, P = 0.1 and 0.5 MPa, whereas gasoline was aerated at P = 0.1 and 0.2 MPa. Based on the peaks in the KE values under the pressures examined in both liquids, the boundaries of the following five regimes were identified: bubbly flow, first transition, second transition, coalesced bubble (4-region flow) and coalesced bubble (3-region flow). As the pressure increases to P = 0.5 MPa in I-butanol, all four transition velocities shift to higher superficial gas velocity, U-G. In addition, in gasoline at P = 0.2 MPa and u(G) <= 0.017 in s(-1), the existence of a chain bubbling regime was detected, whereas in I-butanol at P=0.5 MPa and u(G) <= 0.02 m s(-1), both laminar and turbulent chain bubbling subregimes were identified. It was found that in I-butanol under ambient pressure, the second and fourth transition velocities occur earlier than in gasoline.