The goal of this study was to determine whether a new internal bioartificial liver utilizing porcine hepatocytes can perform detoxification and other metabolic functions. Such a system might aid in treating patients with moderate to severe liver failure and prolong patient survival until a matching organ is found for transplantation. Porcine hepatocytes were attached to a microcarrier and an internal artificial liver was constructed by perfusing the hepatocytes into a polysulfon hollow fiber. The 4 experimental groups were: (a) control group, (b) microcarrier group, (c) hollow fiber group, and (d) internal bioartificial liver group. Viability of hepatocytes, alanine aminotransferase (ALT) and lactate dehydrogenase (LD) activities in the medium, urea production, diazepam transformation, protein synthesis, and glucose-6-phosphatase activity of cells were monitored during a 7-day culture period. Viability of porcine hepatocytes in the internal bioartificial liver group was maintained at >80% during the culture period, and alanine aminotransferase and lactate dehydrogenase activities did not fluctuate significantly. These enzyme activities were significantly lower in the internal bioartificial liver group than in the control or microcarrier groups. Urea production, diazepam transformation, [3H]-leucine incorporation, and glucose-6-phosphatase activity were significantly higher in the internal bioartificial liver group than in the control and hollow fiber groups. These results show that the new internal bioartificial liver produces small amounts of ALT and LD and exhibits detoxification and protein synthetic functions.