The transradial approach for catheterization is becoming increasingly more popular. At present, the choice of the right or left radial artery depends on the operator's preference. We examined how the laterality influenced the effectiveness of the approach. Employing Judkins-type catheters, we performed coronary angiography in 232 patients with the left approach and in 205 patients with the right approach. Although access time did not differ between the two groups of patients, the duration of catheter manipulation was shorter in the left- than in the right-approach group (11.7 +/- 5.9 vs. 9.8 +/- 4.4 min; P < 0.001). Because of the shorter duration of catheter manipulation, the total procedural duration was shorter in the left-approach group (13.7 +/- 6.4 vs. 11.4 +/- 4.8 min; P < 0.001). The fluoroscopy time was shorter in the left- than in the right-approach group (3.7 +/- 2.5 vs. 5.0 +/- 3.3 min; P < 0.001). The amount of contrast material did not differ between the groups (79 +/- 27 vs. 83 +/- 25 ml). The rate of guidewire usage to engage the coronary ostium was higher in the right- than in the left-approach group because of the severe tortuosity of the right subclavian artery (20/205 vs. 0/232; P < 0.001). Thus, for operators with significant experience, the left radial approach may provide increased procedural efficacy for coronary angiography compared to the right radial approach.