An alternative way for determining the oxygen mass transfer coefficient, k(L)a, based upon the traditional dynamic method, is proposed. The oxygen material balance equation in the liquid phase is integrated after insertion of the oxygen probe response time (first order type), and k(L)a values are determined by employing Marquardt's algorithm, considering as a weighting factor the model's sensitivity with respect to k(L)a. Bench-scale fermentations of Aspergillus awamori, performed under different agitation (300-700 rpm) and aeration conditions (0.2-0.6 vvm), were utilized for calculating k(L)a values (0.0283-0.0874 s(-1)), employing three methods: two so-called traditional, the gas balancing and the dynamic methods, and the one proposed here. The latter method is shown to be as reliable as the aforementioned methods but is easier to apply when the oxygen level in the reactor is above the critical value.