BACKGROUND AND OBJECTIVES: Transradial coronary angiography and intervention are increasing in frequency due to lower major vascular access site complications and the potential for early mobilization. However, the small size of the radial artery (RA) is a major limitation of this technique. A sheathless guiding catheter (GC) has recently been introduced that has a 1-2 French smaller diameter compared with the corresponding introducer sheath. This catheter also has a hydrophilic coating along its entire length. We evaluated the feasibility of using a sheathless GC in patients who have small radial arteries. SUBJECTS AND METHODS: The procedural results were evaluated in patients with small radial arteries (diameter <2.3 mm) who underwent transradial coronary intervention using a sheathless GC. RESULTS: A total of 25 (male: 9) patients with 29 lesions were enrolled. The mean RA diameter was 1.81+/-0.26 mm. 44% of the patients had stable angina and 50.0% had acute coronary syndrome. The procedural success rate was 93.1%. Two patients (6.9%) had chronic total occlusive lesions that could not be crossed with a guide-wire despite good guiding support. An intravascular ultrasound could be used for all of the treated lesions. Multi-vessel intervention was performed in 29.2% of the patients. Two bifurcated lesions were treated with a kissing balloon technique, and one with a modified T-stenting technique. No catheter related complications were reported. CONCLUSION: The use of a sheathless GC is feasible in patients with small radial arteries without catheter related complications.