We have assessed the bacteriological safety of a system of intravenous feeding by culturing catheters on removal, swabs taken from the catheter's skin entry sites, and samples of infusion fluid. Among 38 treatment periods using 51 catheters over 1551 patient days, septicaemia due to Staphylococcus aureus was observed in one treatment period and bacteraemias due to Staphylococcus albus and Diphtheroid species in two others. The Staph. aureus and the diphtheroids probably gained access via the skin entry site along the outside of the catheter. The origin of the Staph. albus was uncertain. Parenteral nutrition over extended periods can be a safe procedure if aseptic precautions are taken. The importance of the catheter's skin entry site as a source of contaiminating organisms is emphasised.