We studied the results of prolonged intravenous therapy with antibiotics through a central venous silicone-elastomer catheter that had been peripherally inserted in thirty-five orthopaedic patients. The catheters remained in place for an average of twenty-nine days (range, five to seventy-four days). The 20-gauge (one-millimeter-diameter) catheters used in our study were smaller in diameter than the triple-lumen catheters or the double-lumen Hickman catheters used in previous studies. The catheters in our study were left indwelling for as long as, or for longer than, those in other studies. Our patients had no serious complications related to the insertion or use of the catheter. However, three (8 per cent) of thirty-eight inserted catheters failed mechanically and had to be removed. Two additional catheters (5 per cent) were removed because the lumen became plugged. One catheter in each of these groups was not replaced, because a catheter was no longer necessary. We believe that the problems with the catheters were related to the small diameter of the tubing that was used in our series. Use of the small-diameter catheter reduces the risk of cardiac tamponade and other complications associated with catheters that have larger diameters, and small-diameter catheters can remain indwelling for a long time. The peripheral route of insertion eliminates the risk of pneumothorax associated with the subclavian route of placement and allows for greater ease of insertion. In addition, the use of catheters made of silicone elastomer reduces the risk of thrombosis and infection, which are associated with catheters made of polyethylene.(ABSTRACT TRUNCATED AT 250 WORDS)