Fatty infiltration of the liver with cholestasis is one of the complications of total parenteral nutrition (TPN). The casualty has not yet been determined. It seems probable, however, that these alterations could be prevented when a mixture of medium- and long-chain triglycerides (MCT/LCT) is used as fat component of TPN instead of the application of long-chain emulsions (LCT) alone. To determine whether this could be demonstrated also morphologically in man, 14 patients needing TPN (25 kcal/kg BW x d, CH 45%, F 35%, P 20%) were examined with ultrasound in order to compare liver-size and grey-scale value before and after 7 days of TPN. Seven of the patients were randomly given as their fat-intake an MCT/LCT-emulsion, the other 7 LCT exclusively. There were no changes in liver size and grey-scale value in the MCT/LCT-group, whereas both parameters showed a significant rise in the patients with LCT (size: 10.4 +/- 1.4 to 11.5 +/- 1.4 cm; grey-scale value: 9.3 +/- 1.0 to 11.6 +/- 0.7). These data suggest that TPN, administered with a mixture of MCT/LCT emulsions as fat component, could reduce the risk of hepatic dysfunction such as cholestasis and fatty infiltration of the liver.