Objectives: The purpose of this study was to define the pre-operative angiographic variables that could influence graft patency and flow pattern. Background: Saphenous vein grafts (SVG) and pedicled right gastroepiploic artery (RGEA) grafts are routinely used to revascularize the right coronary artery (RCA). Little is known about the predictive value of objective pre-operative angiographic parameters on the 6-month graft patency and on the interest of these parameters to select the optimal graft material in individual cases. Methods: We prospectively enrolled 172 consecutive patient candidates for coronary revascularization. Revascularization of the RCA was randomly performed with SVG in 82 patients or with the RGEA in 90 patients. Both groups were comparable with respect to all pre-operative continuous and discrete variable and risk factors. All patients underwent a systematic angiographic control 6 months after surgery. Pre-operative angiographic parameters included minimal lumen diameter (MLD), percent stenosis and reference diameter of the RCA measured by quantitative angiography (CAAS II system, Pie Medical, Maastricht, the Netherlands), location of the stenosis, run off of the RCA, and regional wall motion of the revascularized territory. Results: A significant difference in the distribution of flow patterns was observed between SVG and RGEA. In multivariate analysis, graft-dependent flow pattern was significantly associated with both MLD and percent stenosis of the RCA in the RGEA group but with percent stenosis only in the SVG group. In the RGEA group, the proportion of patent grafts was higher when MLD was below a threshold value lying in the third MLD quartile (0.77 to 1.40 mm). Conclusions: Pre-operative angiography predicts graft patency in RGEA, whereas the flow pattern in SVG is significantly less influenced by quantitative angiographic parameters.