Cells from primary porcine hepatocytes (PPH) and the immortalized human hepatoma cell line C3A are both used in bioartificial liver support systems (BALSS). In this work the viability and metabolic capacity of PPH and C3A cells cultured in different media were compared. Also, because the cells come into direct or indirect contact with human blood components in BALSS, the effects of human complement on survival and functions of the cells was evaluated. For short-term culture, maintenance of PPH viability was essential for retention of P450IA1 activity (r = 0.882, p < 0.01) and effective ammonia clearance (r = -0.791, p < 0.01). When cell viability was below 60% P450IA1 activity could not be recorded and nitrogen elimination activity significantly diminished. In contrast to PPH, ammonia levels were markedly increased for C3A cells in all culture media tested (p < 0.01). Ammonia increase correlated with C3A viability (r = 0.896, p < 0.05). PPH metabolic function was superior to that of the C3A cell line when evaluated by P450IA1 activity, ammonia removal, and amino acid metabolism. When PPH were incubated in human plasma (HP) or human serum (HS) there was rapid and irreversible deterioration of viability occurring within 9 h. This toxic effect could be prevented by the inactivation of complement. When sodium citrate dissolved in dextrose was added to medium, there was considerable damage to both PPH and the C3A cell line. However, there was no demonstrable toxic effect when hepatic cells of either type were exposed to heparin. We conclude that PPH cultivated in complement-inactivated HP or HS are to be preferred to C3A for clinical application of BALSS, and that heparin should be preferred for anticoagulation in BALSS.