Volumetric liquid phase mass transfer coefficients were measured by means of desorption experiments of dissolved oxygen in several highly Viscous liquids in bubble columns. Gas hold LIPS were also measured by use of the same bubble Columns. These measurements were carried Out under the various conditions of the column diameter, liquid depth and liquid viscosity in the range where the superficial velocity of the gas is less than 5 mm/s. The volumetric mass transfer coefficient was found to decrease with increasing liquid depth, but it showed constant values if the ratio of the liquid depth to column diameter exceeded a certain value. From these results, a correlation equation which was applicable to a ide range of operating conditions was proposed. The gas hold-up was found to increase with increasing liquid viscosity, independently of the liquid depth, and to be expressed well by the empirical correlation equation proposed in this work.