We examined vasospasms of the radial artery after a transradial approach was used for coronary angiography or angioplasty. In forty-eight patients (39 males and 9 females), arteriography of the radial artery was initially performed just after the transradial approach was used for coronary angiography and/or angioplasty. Then, five months later, a second arteriography of the radial artery was obtained after a transbrachial approach was used for coronary angiography. First and second arteriographies were compared to evaluate vaso-spasms of the radial artery. In the present study, more than 75% stenosis in the radial artery, 25-75% stenosis, and less than 25% stenosis were tentatively defined as severe spasms, moderate spasms, and mild spasms, respectively. In arteriographic studies on the radial artery, twenty-four patients (50%) had severe radial artery spasms, eleven patients (23%) had moderate spasms, and thirteen patients (27%) had mild spasms. The diameters of both the proximal and distal radial arteries in the severe spasm group were significantly smaller than those in the mild and moderate spasm groups (proximal site: severe group 2.39 +/- 0.70 mm versus mild group 2.98 +/- 0.46 mm, P < 0.05, and moderate group 2.96 +/- 0.77 mm, P < 0.05, distal site: severe group 2.26 +/- 0.60 mm versus mild group 2.73 +/- 0.47 mm, P < 0.05, and moderate group 2.86 +/- 0.71 mm, P < 0.05). We concluded that vasospasms of the radial artery occurred in most patients after the transradial approach. Furthermore, severe radial spasms were strongly correlated with the size of the diameter of the artery.