A new type of steerable guiding catheter is described for use in percutaneous transluminal coronary angioplasty (PTCA). It is simple to use and externally steerable. The catheter incorporates a steering system by means of which the catheter tip can be made to assume the form of either a right or left Judkins catheter or to be fixed in any intermediate configuration, entirely through external manipulation. We used this new guiding catheter to perform PTCA on 15 patients. Single lesions were found in the left anterior descending branch in seven patients, in the right coronary artery in four, and in the circumflex artery in two, whereas stenosis of a coronary bypass graft was found in two patients. Angioplasty was successful in all cases. There were no complications, during either the procedure or the postoperative hospitalization. The steerable guiding catheter described here may prove useful for PTCA in cases where a conventional catheter cannot be placed accurately or in cases with multi-vessel coronary disease.