Two methods of preventing intravenous catheter-related thrombophlebitis of the jugular vein, using clinical and ultrasonographic criteria, were compared. The first method consisted of minimising bacteriological contamination by the preparation of the skin as if for surgery. The second method involved the daily subcutaneous administration of low doses of heparin to decrease procoagulant activity. The results showed that the preparation of the skin before the placement of an indwelling catheter in the jugular vein and adequate daily maintenance of the catheter were of great importance in the prevention of thrombophlebitis induced by bacteriological contamination. The use of heparin should be limited to cases that require long-term catheterisation or are predisposed to thrombosis or other clotting abnormalities.