Mathematical models have been developed to describe the performance of continuous counter-current expanded bed adsorbers, novel devices for continuous purification of proteins from unclarified preparations of disrupted cells. Predictions from the models have been compared with experimental data from small scale systems. These models have been used to illustrate how the performance of the adsorber can be optimised by appropriate choices of contactor dimensions and other operation conditions. In addition, the work also illustrates how the device can be expected to deliver superior performance when compared to more conventional counter-currently operated systems, such as series of mixer-settler units.