Isolated hepatocytes prepared from Wistar rats by mechanical means were infused into the liver of congenitally jaundiced Gunn rats. Red cell survival was determined in the recipients and their total plasma bilirubin was measured just before and 20 days after transplantation. Similar measurements were made in transplanted Gunn rats receiving the immunosuppressant drug cyclophosphamide at 5 mg/kg/day and in a group of splenectomized Gun rats. Red cell survival was significantly prolonged in all transplanted rats and in the splenectomised group. Total plasma bilirubin also fell significantly in all three groups by up to 25%, a change we attribute to reduced red cell turnover, haemoglobin synthesis and hence reduced bilirubin synthesis. Blockade of the splenic reticuloendothelial system by hepatocyte debris is suggested as a possible cause.