Oxygen absorption rates were measured to determine volumetric coefficients of gas-liquid mass transfer coefficients k(L)a in gas-liquid and gas-liquid-solid upward flows through a vertical tube. The liquid was deionized water or aqueous glycerol solution, and the solids were glass beads or polystyrene beads. The dependencies of k(L)a on gas velocity, liquid velocity, temperature, solid material, and solid concentration were examined. The experimental results were correlated with empirical equations. The mechanisms of the solid loading effect are discussed.