Objectives Our aim was to compare the effectiveness between right radial approach (RRA) and left radial approach (LRA) by means of a randomized study in a large unselected patient population undergoing diagnostic coronary angiography. Methods Totally, 1,000 patients were randomized to undergo to RRA (n = 500) or LRA (n = 500). Procedure success was defined as coronary angiography completed with the initial radial artery approach without changing to another route. Performance of the procedure: Total procedural duration, the number of catheters and guidewires used were recorded. Safety of the procedure: The parameters collected for radiation exposure were dose area product (DAP) and fluoroscopy time. Results The percentage of success was not different between the two aproaches (LRA, 94.0%; RRA,93.8%; P = 0.96). The crossover rate to femoral was low, accounting for 38 cases (3.8%), without differences between RRA and LRA (20 and 18 cases, respectively, P > 0.05). An almost triple incidence of operator-reported subclavian tortuosity in the RRA compared with LRA was observed (44 cases vs. 15 cases, P < 0.001). With respect to the total procedural duration there was no difference between those two aproaches (LRA, 8.54 +/- 4.09 min vs. RRA, 8.63 +/- 5.20; P = 0.772). However, the fluoroscopy time was significantly shorter via the LRA compared with RRA (2.76 +/- 2.00 min vs. 3.08 +/- 2.62 min; P = 0.029). Conclusions LRA for coronary angiography is associated with the same success rate and procedural duration time compared with RRA. However, the fluoroscopy time is significantly shorter in favor of LRA. (C) 2012 Wiley Periodicals, Inc.