In the present study, the stabilizing effect of dextrans as additives on the denaturation and inactivation of glucose oxidase (GOD) was investigated. Three different molecular weighted dextrans (M(w) 17.5, 75, 188 kD) were used with different concentrations. Dramatically increased enzyme activities were measured after one hour of incubation of enzyme with additives between 25-40°C in water bath. Highest activity value was measured with 75 kDa molecular weighted dextran (in concentration 30% w/v) at pH 5. Dextran as an additive supplied a long shelf-life to the enzyme at 4°C. In the presence of the 75 kDa dextran, the enzyme was more stable and its activity was increased 2.7-fold at 30°C. In addition, dextran protected GOD against inactivation by a n-heptane/aqueous buffer-stirred system.