The Kolmogorov entropy (KE) algorithm was successfully applied to single source gamma-ray Computed Tomography (CT) data measured by three scintillation detectors in a 0.162 m-ID bubble column equipped with a perforated plate distributor (163 holes X circle divide 1.32 center dot 10(-3) m). The aerated liquid height was set at 1.8 m. Dried air was used as a gas phase, while Therminol LT (rho(L) = 886 kg m(-3) mu(L) = 0.88 center dot 10(-3) Pa s, sigma = 17 center dot 10(-3) N m(-1)) was used as a liquid phase. At ambient pressure, the superficial gas velocity, u(G), was increased stepwise with an increment of 0.01 m s(-1) up to 0.2 in s(-1). Based on the sudden changes in the KE values, the boundaries of the following five regimes were successfully identified: dispersed bubble regime (u(G) < 0.02 m s(-1)), first transition regime (0.02 <= u(G) < 0.08 m s(-1)), second transition regime (0.08 <= u(G) < 0.1 m s(-1)), coalesced bubble regime consisting of four regions (called 4-region flow; 0.1 <= u(G) < 0.12 ms(-1)), and coalesced bubble regime consisting of three regions (called 3-region flow; u(G) > 0.12 m s(-1)). The KE values derived from three scintillation detectors in the first transition regime were successfully correlated to both bubble frequency and bubble impact. The latter was found to be inversely proportional to the bubble Froude number. The KE model implies that the bubble size in this particular flow regime is a weak function of the orifice Reynolds number (d(b) = 7.1 center dot 10(-3) Re-0(-0.05)).