To determine the suitability of 6 French catheters for quantitative coronary arteriography, the relative accuracy and reproducibility of one type of these catheters was compared to that obtained with standard 8 French catheters in 20 stenoses. Duplicate injections with polyurethane 6 French catheters were obtained using hand and power injection technique with cineangiographic acquisition (four 6 French catheter injections total per stenosis). Measurements of both percent diameter stenosis and absolute dimensions were compared to those obtained with hand injection and cine acquisition using 8 French catheters as a "gold standard." While the reproducibility of dimension determination with the 6 French catheter was generally similar to that obtained with the 8 French catheter (0.27 +/- 0.23 mm for absolute diameter and 8.1 +/- 7.4% for percent diameter stenosis), accuracy was significantly less for the 6 French catheter for measurement of absolute dimensions. Thus, while apparently well suited for serial measurements of the same stenoses, 6 French catheters may not be as accurate in the determination of absolute artery dimensions as 8 French catheters.