The possibility of using commercially available infusate solutions as a culture medium for hepatocytes was investigated in primary monolayer cultures of rat hepatocytes. The addition of Ca2+ to the infusate medium was necessary for hepatocytes to express their albumin secreting ability. The infusate medium supplemented with hormones (10(-7) M insulin and 10(-7) M dexamethasone) and Ca2+ (72.5 mg/l) allowed hepatocytes to produce albumin of an amount comparable to that produced in Williams' E medium. The activity of released lactate dehydrogenase (LDH) was kept at a low level throughout the cultivation in the infusate medium.