The volumetric gas/liquid oxygen mass transfer coefficients, k(L)a were measured by a modified dynamic method in two bubble columns with D less than or equal to 0.10 m i, with single tube and porous plate as gas distributors using water and starch solutions of five concentrations as liquid phase and air as gaseous phase. The measured k(L)a values were found to be dependent on gas superficial velocity, liquid pseudoplasticity, H/D ratio, sparger configuration and axial position in the column. Neither dependence was found on column diameter.