Eighty-eight intravenous cannulae with valved injection sideports were examined bacteriologically after approximately three days (64-80 h) normal clinical use. Three methods of culture of the cannulae were used, which distinguished contamination of the outer and inner surfaces as well as detecting bacteria remaining on the inner cannula surface following a washing procedure of the lumen. Of the cannulae sampled, 40.9 per cent were found to be contaminated on their inner surfaces and no correlation was obtained between use of the sideport and contamination of the cannulae at this site. It was concluded that contamination of a cannula lumen did not necessarily result in bacteraemia.