A new 6 French (F) guiding catheter with a large, teflon-coated internal lumen (4.2F) was developed, permitting use of the standard ultralow profile (less than 3F) over-the-wire system. This small coronary angioplasty system (6F-PTCA) was evaluated in 48 lesions in 45 of 137 patients (33%) who underwent coronary angioplasty between September 1990 and January 1991. The mean age was 64 years (range 49 to 82); 37 (82%) were male. The procedure was via the brachial artery in 28 patients (62%). The overall primary success rate was 96%. It was 100% via the brachial artery and 90% via the femoral artery. There were no major complications. The puncture compression time with the 6F-PTCA via the brachial artery and via the femoral and with 8F-PTCA via the femoral was 3.8, 9.6, and 16.9 hr, respectively (P less than 0.001), although the procedure time of the 6F-PTCA via brachial and via femoral and of the 8F-PTCA was not significantly different. The mean hospital stay was 3.1, 4.5, and 5.5 days, respectively (P less than 0.01). A small hematoma occurred in 2 patients (4.4%) after the 6F-PTCA and in 3 (3.3%) after 8F-PTCA, and a large hematoma (greater than 5 cm) was noted in 7 patients (7.6%) after 8F-PTCA. These results indicate that coronary angioplasty using the over-the-wire system through the new 6F guiding catheter is technically feasible. Moreover, this approach, especially when advanced via the brachial artery, could shorten the hemostasis time and facilitate early ambulation.