The primary requirement of cells in a liver support system is the preservation of the in vivo metabolic functions that prevent or decrease the progress of hepatic encephalopathy (HE) by providing interim support to liver failure patients. While rodent hepatocytes offer a model for liver assist device (LAD) research, their limited number per animal prohibits direct scale up to human devices. Healthy human liver cells are seldom available in adequate numbers to support clinical LAD use; consequently, a large animal source of liver cells is needed. The study presented here explored the potential of porcine hepatocytes to proliferate and maintain metabolic function in vitro. Porcine hepatocytes were isolated from approximately 12 kg swine by a modification of Seglen's method. Hepatocytes cultured up to 10 days were shown to metabolize ammonia and maintain both Phase I and II detoxification functions. In addition, the cultures showed proliferative activity both as an increase in total protein content and by thymidine incorporation. Immunocytochemical staining identified cell proliferation through Day 4 to be primarily hepatocytes while Days 6 and 10 showed nonparenchymal cells to be increasing. The detoxification functions measured showed peak activity on Day 4 and gradually declined through Day 10. The ability of porcine hepatocytes to proliferate and maintain a diversity of hepatic functions in culture strongly suggests their potential for use as the biological component of artificial LADs.