Mechanical stress caused to transfected Chinese hamster ovary (CHO) suspension cells by reusable and single-use magnetically levitated, bearingless centrifugal pumps was investigated. Cell death rates were determined for different pump speeds and compared with data from a peristaltic and a 4-piston diaphragm pump. Furthermore, the fluid distribution inside the PuraLev (R) 200pump was modeled using computational fluid dynamics. The results reveal considerably lower mechanical stress to CHO cells caused by the magnetically levitated bearingless centrifugal pumps than by the peristaltic and diaphragm pump.