Gas holdups, volumetric mass transfer coefficients for oxygen and specific interfacial areas were determined in a bubble column at 1 and 8 bar pressure. Then was found to be a strong increase of these parameters with gas density. Gas disengagement measurements were determined using the fractions of small and large bubbles. The addition of 2 vol.% glass beads had only minor effects. The liquid-side mass transfer coefficient k(L) was about 4 x 10(-4) m s(-1) independent of the pressure.