OBJECTIVE: To compare the safety and efficacy of 5French (5F) and 6French (6F) guiding catheters in patients undergoing transradial coronary intervention (TRI). METHODS: A total of 185 patients were included from February 2009 to March 2010, and relevant data were collected and entered into the database, including baseline clinical information of patients, size of the guiding catheter, target vessel, characteristics of the target lesion, success rate of the procedure, reasons for procedure failure, success rate of transradial coronary intervention procedures and reasons for failure, rate of major adverse cardiovascular events during the patients’ hospitalization, and rate of postoperative radial artery occlusion. RESULTS: A total of 185 patients with a mean age of (57±10.9) years (33-81 years) underwent 195 transradial coronary interventions were included; 54 patients were included in the 6F-guided catheter group, with 56 procedures performed to treat 89 lesions, and 138 patients were included in the 5F-guided catheter group, with 146 procedures performed to treat 231 lesions. aHA B2/ There was no statistically significant difference in the proportion of type C lesions between the two groups (43.7%/29% in the 5F group versus 46.1%/34.6% in the 6F group, P>0.05), but chronic occlusive lesions, bifurcation lesions, and calcified lesions were significantly less in the 5F group than in the 6F group (5.2% versus 14.6%, P=0.005; 23.1% versus 37.1%, P=0.012; 10% versus 47.2%, P<0.001); the differences between the groups were not statistically significant (P>0.05) in the operative time ((45±21) min versus (46±19) min), operative X-ray exposure time ((15±12) min versus (16±13) min), and the amount of contrast agent used ((140±45) ml versus (156±56) ml), but However, there was a tendency to reduce the amount of contrast agent used in the 5F group (P=0.066); there was no statistically significant difference in the length of stay ((1.40±1.26) days compared with (1.29±0.69) days) and the success rate of the procedure (95.2% compared with 94.6%) between the groups (P>0.05); one patient in the 5F group had postoperative radial artery occlusion and no patient in the 6F group had postoperative radial artery occlusion (P=1.0). One case of stroke occurred in the 5F group. CONCLUSIONS: Transradial coronary intervention, even for complex and high-risk coronary lesions, is effective and safe with a 5F-guided catheter, with a procedural success rate no lower than that of the routinely used 6F-guided catheter, and with a low risk of radial artery occlusion and adverse cardiovascular events during hospitalization; switching to a 5F-guided catheter for coronary intervention is an attractive option.