Radial artery access improves the patient's well-being, permits earlier ambulation and diminishes vascular complications after cardiac catheterization. Using the same catheter to study the left and right coronary arteries may facilitate the technique. In a cohort of 100 patients we prospectively analyzed the possibility of studying both coronary arteries with a Judkins left 3.5 catheter. The variables studied were percentage of successful access, complications, and procedural time from insertion of the guiding catheter to the end of ventriculography. It was possible to catheterize both coronary arteries with the same catheter in 94 cases (94%) with a procedural time of 16.7 (6.8) min. In 6 patients a JR4 catheter was required, in one of them due to severe spasm of the right coronary artery ostium and due to impossibility to catheterize the ostium in the other 5. There were no cases of severe radial artery spasm.