The use of 6F catheters has been validated for coronary angiography. The use of small-caliber catheters is a more recent development. The aim of this study was to assess the feasibility, the cost and complications of coronary angiography using the femoral approach with 4F catheters. The authors undertook a randomized prospective study of 4F Care Infiniti catheters (N = 100) and 6F Spertorque Plus catheters (N = 100) in hospitalised patients. Criteria of non-inclusion were valvular pathology, acute myocardial infarction, aorto-coronary bypass or aorto-femoral bypass procedures. No statistical difference was observed between the two groups with respect to feasibility, to duration of the procedure, or of irradiation or to cost. The quality of the angiograms was good except in one patient in the 4F group; 4 patients in the 6F group required a 4F catheter to complete their examination. Left ventricular catheterisation was more difficult with 4F catheters (p = 0.016). Use of 4F catheters was associated with injection of significantly less contrast (p = 0.00007), reduced the duration of compression (p < 10(-6)) and its complications (p = 0.004). The authors conclude that 4F catheters are safe and well tolerated. They are associated with less patient morbidity, without any loss in quality of the angiogrammes. Other studies in valvular heart disease and after coronary bypass surgery should lead to the generalisation of their use in all coronary patients.