The effects of process variables on the volumetric liquid phase mass transfer coefficient of oxygen, k(L)a, in a stirred bioreactor were investigated by the static gassing-out method. The process variables chosen were impeller speed. air flow rate, temperature. viscosity and loading (%) of biomass support particles (BSP). The k(L)a value was obtained as 2.766 min(-1) in distilled water at process variables such as stirrer speed 300 rpm, air flow rate 0.3 1 min(-1), temperature 37 degreesC and pH 7. By using the same process conditions, k(L)a values obtained in glycerol (50%) + distilled water, distilled water containing BSP (loading 25%, particle volume 0.1625 cm(3)) and glycerol (50%) + distilled water containing BSP (loading 25%, particle volume 0.1625 cm(3)) were 1.383, 0.933 and 0.450 min(-1), respectively. The exponents representing dependence of k(L)a on the process variables were also obtained by using oxygen absorption data. then these values were compared with literature values.