The present review discusses hepatocyte sources for a bioartificial liver. Intended requirements for cell sources are for example: synthesis of plasma proteins, detoxification and regulation. The need for highly differentiated hepatocytes is stressed. Furthermore, the gap between this objective on the one hand and the real possibilities as they appear today on the other is shown. Alternatives to primarily isolated hepatocytes are discussed, thereby elucidating the limits of established cell lines. In summary, it is postulated that the results expected from a bioartificial liver, are closely related to the source and type of cells used.