The transradial approach has currently been accepted as an alternative entry method for coronary angiography and angioplasty. Vascular complications of this method were evaluated by 2-dimensional echo and color Doppler ultrasonic studies in 162 patients before, early (2+/-2 [mean+/-SD] days), and late (95+/-29 days) after catheterization. Mean age was 64+/-10 years, and 103 were men. Coronary angioplasty was performed in 59 patients (79 lesions) with angiographic success in 92%. Early after the procedure, segmental stenosis was noted in 35 patients (22%) and no flow in 15 patients (9%). Late after the procedure, segmental stenosis was noted in 2, diffuse stenosis in 36 (22%), and no flow in 8 (5%) patients. The cessation of radial artery pulse was unpalpable in only 2% of cases, whereas radial flow by color Doppler was undetectable in 9% early after the procedure. Late after the procedure, recanalization was observed in 60% of these occluded cases. Thirty-three of 86 patients (38%) with no flow or diffuse stenosis had radial artery diameters smaller than the sheath diameter, and 11 of 76 patients (14%) had radial artery diameters larger than the sheath diameter (p <0.01). Multivariate analysis revealed risk factors for vascular complications: (1) Radial artery diameter before the procedure was one of the significant and independent determinants of no flow both early (p = 0.06) and late (p = 0.004) after the procedure. (2) The difference in radial artery diameter and sheath size was related to the occurrence of diffuse stenosis late after the procedure (p = 0.003). (3) Diabetes mellitus was related to no flow (p = 0.05) or diffuse stenosis (p = 0.11) late after the procedure. Thus, ultrasonic evaluation of the radial artery was useful in selecting both an access route and an appropriate size of the sheath to determine early and late vascular complications.