The XDR reactor can be and is currently used in perfusion processes and there are a variety of perfusion systems that can be applied. There are a couple of features that should be remembered for this application. The first one is the connections between the perfusion apparatus to the bioreactor, specifically draw and return. Aseptic connectors or tube welding can be used to make these connections. A second aspect to consider is the choice of using a pump or an alternative fluid transfer mechanism to withdraw fluid. The fluid control is done by setting the system control for feed or harvest based upon vessel weight. Other than some of these features, the technology and operation are consistent with traditional perfusion mode.