A group of 460 patients was considered in our prospective study of assessment of the efficiency and safety of 6F (internal diameter 0.062 inches) guiding catheters to perform elective percutaneous coronary angioplasty by the femoral approach by using conventional balloon systems. The patients were randomly assigned either a 6F guiding catheter (first group, n = 231; 247 coronary lesions), or a 7F or 8F guiding catheter (second group, n = 229; 252 coronary lesions). The exclusion criteria were the ongoing myocardial infarction, the marked reduction of left ventricular function, and the decision to treat the lesion with a device not fitting the 6F guiding catheter. The angioplasty success rates (87% in the 6F group vs 88% in the 7F or 8F group) and the stent implantation rates (21% vs 25%) were similar in both groups. The ischemic complication rates (death, 2 vs 1 ) were also similar. The incidence of the femoral complications was significantly less important in the 6F group than in the 7/8F group (13.8% vs 23.5%; p < 0.01). Significant differences also were noted for the procedural time (36 +/- 22 vs 41 +/- 28 min; p < 0.01), the fluoroscopy time (11 +/- 10 vs 14 +/- 4 min; p < 0.05), the volume of contrast injected (136 +/- 68 ml vs 168 +/- 95 ml; p < 0.0001), and the time of femoral compression after the introducer sheath removal (11.7 +/- 9 vs 14.1 +/- 12 min; p < 0.01). Our data suggest that 6F guiding catheters for elective coronary angioplasty are more effective than are the larger diameter catheters. Besides a significant decrease of vascular complications, angioplasty with a 6F guiding catheter reduces the procedural time and the amount of contrast.