The light transmission technique is used to measure interfacial areas in stirred gas-liquid reactors under various conditions of pressure and temperature. Interfacial area increases as pressure increases and in certain cases this increase can be as much as 75% above that obtained under similar operating conditions but at atmospheric pressure. Gas density will increase with pressure and if the gas enters saturated with solvent there will be a further increase in density due to this factor. This increase in gas density increases the kinetic energy of the gas at the inlet sparger. The increase in interfacial area can be correlated with this kinetic energy. Calderbank's correlation for predicting interfacial area has been independently verified. A modification of this correlation is proposed to account for the effects of pressure and temperature. The modified correlation has a wide range of applicability. The data presented has potential use in establishing better design criteria for gas-liquid contacting in pressurized stirred vessels.