The efficacy of 6 French guiding catheters for angioplasty of chronic total coronary occlusions was evaluated in 61 consecutive patients. The duration of the occlusion was determined angiographically, or estimated from an index clinical event. Endpoints were procedural success, defined as recanalization with less than 50% residual stenosis without major complications; and the need to change to larger-sized guiding catheters. Recanalization was attempted in 62 chronic total occlusions; 35 were located in the left anterior descending coronary artery, 18 in the right coronary artery, and 9 in the left circumflex coronary artery. The mean duration of the occlusion was 6.0 6 6.6 months; the range was 2-39 months. Lesion morphology included abrupt or diffuse occlusion (55%), a side branch originating at the occlusion (47%), and bridging collaterals (23%). Death, urgent coronary bypass surgery, or myocardial infarction did not occur. Recanalization was successful in 51 of the 62 total occlusions (82%); 49 were completed successfully with a 6 French guiding catheter, and 2 were successful after changing to a larger-sized guiding catheter (which was required for peripheral vessel tortuosity in one patient, and to obtain better back-up support in another). Three other attempts remained unsuccessful after a changing. A total of 12 Palmaz-Schatz stents were implanted in 11 patients for an unsatisfactory result or type C dissection, using the same 6 French guiding catheters. These preliminary findings indicate that 6 French guiding catheters are both effective and safe for angioplasty of chronic total occlusions.