Valuable haemodynamic data can be derived from a properly positioned Swan-Ganz catheter. Unfortunately, a significant number of these catheters will, for one reason or another, become malpositioned. Withdrawing a catheter from a permanently wedged position presents little difficulty. Repositioning may, however, necessitate its advancement, with the attendant risk of bacterial contamination. We have solved this problem by making a protective sleeve from readily available latex drain and tubing, which fits securely over the haemostatic valve of a No. 8F Cordis introducer. Iodine solution is injected into the sleeve to provide a sterile environment for the Swan-Ganz catheter, which can then be repositioned as required without the risk of bacterial contamination, as verified by bacteriological studies.