Four incidents of catheter separation in three patients during left heart catheterization and coronary angiography are presented. In two cases the catheters had been used before. After the second incident, we decided to use angiography catheters once only. All catheter fragments were removed under local anesthesia, and no further complications arose. In all incidents the point of catheter fracture was near the bond between the body of the catheter and its tip. We believe that catheter separation is related to polymer aging. The catheters in the third and fourth incidents were unused, but there was no expiration date on their packages. We recommend that expiration dates be clearly stated on every catheter package, catheter manufactures issue warnings not to use catheters after expiration date, and unused angiography catheters with no expiration date not be used. We also suggest that consideration be given to using catheters once only.