In previous research into hepatocyte transplantation (HTX) the spleen was the preferred acceptor organ for isolated donor hepatocytes. In this study the pancreas was tested as an acceptor organ for HTX. HTX into the pancreas or spleen was performed by injection of 10(7) isolated hepatocytes into the parenchyma of these organs. Intrapancreatic hepatocytes showed good viability 3 months after syngenic HTX as assessed by histological and immunocytochemical parameters. Definite proof of sustained metabolic activity of normal hepatocytes, 3 months after transplantation into the pancreas of congenitally jaundiced rats, was obtained by demonstration of bilirubin conjugates in bile of the recipients: 4.0% of total biliary bilirubin was conjugated. Intrasplenic HTX, however, was more effective and resulted in a conjugated fraction of 17.7% of total biliary bilirubin (p less than 0.001). Reduction of total plasma bilirubin was significant with both methods, but more pronounced in intra-splenic HTX. Bile drainage from the hepatocellular transplant via the pancreatic excretory system into the gut was not observed: conjugated bilirubins were not found in pancreatic juice of HTX-treated jaundiced rats. Intrapancreatic HTX did not adversely affect the host rat; evidence of pancreatitis or diabetes was not found. It is concluded that the pancreas is a suitable acceptor organ for HTX. However, intrapancreatic HTX appears to be less effective than intrasplenic HTX in the treatment of enzyme deficiency disease.