Objectives: It has been known that the presence of tortuous radial artery in patients undergoing transradial coronary angiography may cause undesirable results such as access failure and arterial dissection. Thus, our aim was to investigate the prevalence and predictors of tortuous radial artery in patients undergoing transradial coronary angiography. Methods: We prospectively investigated the tortuosity of radial artery in 158 consecutive patients. The radial angiogram was performed prior to coronary angiogram and the tortuous radial artery was defined as maximal angulation of more than 45 degree of radial artery. To find out the predictors of tortuous artery, we examined the pre- and intra-procedural characteristics such as clinical characteristics, degree of radial pulsation and passage resistance of mini-guide wire. Results: The right radial angiography was easily performed in 154 patients (97.5%) without any complications. The presence of tortuous radial artery was seen in 34 patients (22%). On univariate analysis, old age, female, short stature, overweight, hypertension, and no progression of mini-guide wire were significantly associated with tortuous radial artery. Significant independent predictors of tortuous radial artery by multivariate analysis were old age (OR 3.9���95% CI 1.3 to 12.3���), no progression of mini-guide wire (OR 3.6���95% CI 1.1 to 11.9���), and hypertension (OR 2.9���95% CI 1.2 to 7.1���). Conclusion: These data showed that the presence of tortuous radial artery was noted in 22% of total patients and could be predicted by old age, no progression of mini-guide wire, and history of hypertension.