Background The Rho/Rho-kinase signaling pathway is known to be involved in the pathogenesis of radial artery spasm.The usefulness of fasudil in combination with conventional vasodilating agents has not been fully examined in patients with radial artery spasm.Methods A total of 30 patients (mean age, 61+/-11 years) with documented radial artery spasm during transradial coronary intervention.Radial artery diameter at the spasm site was measured at baseline and after the administration of vasodilator agents in the following order: nitroglycerin(NTG) (200 microg), intravenous fasudil (30 mg, n=15, fasudil group) or saline (n=15, saline group), and again NTG during radial artery angiography.Result The increase in diameter observed following the first NTG administration was found to be similar in the fasudil and saline groups (38.3+/-23.5% and 42.3+/-17.1%, respectively).The additional change in diameter on fasudil treatment (16.9+/-11.2% increase over the diameter after the first NTG administration) was significantly larger than that with saline (-2.8+/-7.6%, P<0.001).The second administration of NTG did not affect the diameter of the spasm site in either group.Conclusions Fasudil further dilated the site of radial artery spasm, which had already been treated with NTG in patients with radial artery spasm.These findings support and extend the previous results that showed the feasibility of employing fasudil as a novel therapeutic approach for radial artery spasm.