Mass transfer, mixing times and power consumption were measured in rigid disposable stirred tank bioreactors and compared to those of a traditional glass bioreactor. The volumetric mass transfer coefficient and mixing times are usually determined at high agitation speeds in combination with sparged aeration as used for single cell suspension and most bacterial cultures. In contrast, here low agitation speeds combined with headspace aeration were applied. These settings are generally used for cultivation of mammalian cells growing adherent to microcarriers. The rigid disposable vessels showed similar engineering characteristics compared to a traditional glass bioreactor. On the basis of the presented results appropriate settings for adherent cell culture, normally operated at a maximum power input level of 5 W m(-3), can be selected. Depending on the disposable bioreactor used, a stirrer speed ranging from 38 to 147 rpm will result in such a power input of 5 W m(-3). This power input will mix the fluid to a degree of 95% in 22 +/- 1 s and produce a volumetric mass transfer coefficient of 0.46 +/- 0.07 h(-1). (c) 2014 American Institute of Chemical Engineers Biotechnol. Prog., 30:1269-1276, 2014