The mass transfer coefficient (k(L))and the value of the interfacial area (a) is used to characterize bioreactor systems for their oxygen transfer capability. The k(L)a value and the mixing time are amongst the most important performance indicators for bioreactors. Their calculation and modeling is extremely complex in highly aerated systems. This paper describes a new methodology for measuring the k(L)a value to accurately determine the coefficient. The valuable insights obtained allow for improved bioreactor characterization, thus, making it easier to meet regulatory requirements. Furthermore, examples outlining the benefits in the practical application of the new methodology are presented.