Abstract: Artificial liver devices and methods for using the devices to purify a biological fluid are disclosed. The methods include the use of living hepatocytes (23) which are either unattached or attached to inert carriers and suspended in a cell culture medium which circulates in the devices with the hepatocytes (23). Blood or plasma passes on one side (7?) of semi-permeable membranes, on the other side (7) of which is the cell culture medium and across which is a concentration and/or pressure gradient. Solutes diffusing across the membrane into the cell culture medium are metabolized by the hepatocytes (23) and/or captured by additional removal means (4). Those undesirable substances which do not diffuse out of the blood or plasma into the hepatocyte containing culture medium are captured by additional removal means (50).