The radial artery has been increasingly used for its favorable safety profile. However, no conclusive data are available on the optimal sheath size. In particular, it is seemingly difficult to weight both advantages and disadvantages of narrower versus larger sheaths size. Despite several studies were performed to compare the use of 6-Fr to the smaller 5-Fr sheaths, these were mostly small, single center-studies, yielding various results.We performed a comprehensive meta-analysis of all available studies comparing the use of 5-Fr versus 6-Fr sheaths in coronary procedures through the TRA.Studies comparing a 5-Fr versus a 6-Fr sheaths were searched for in PubMed, the Cochrane Library, and ISI Web of Knowledge databases.Studies were deemed eligible if they only included patients undergoing transradial cardiac catheterization with 5-Fr or 6-Fr system and reported at least one of these parameters: contrast dye volume, procedural success, procedural time, access complications, radial artery occlusion, and bleedings.Odds ratio (OR) and the mean difference (MD) were respectively used for dichotomous and continuous variables as summary measures. Both the random-effects model and the fixed effect models were used for computation of meta-analyses. Heterogeneity was assessed by means of the Cochrane Q test. Metaregression was calculated using the unrestricted maximal likelihood random effects model.The use of a 5-Fr system is associated with a significant lower contrast medium administration (MD = -22.20 [-36.43 to -7.96], P < 0.01) and significantly reduces bleedings (OR = 0.58 [0.38-0.90], P = 0.02), without compromising procedural success (OR = 0.95 [0.53-1.69], P = 0.86) or procedure length (OR = 0.55 [-2.58 to 3.69], P = 0.73), compared to the 6-Fr system. Despite no significant difference was observed between the groups (OR = 0.88 [0.50-1.56], P = 0.67), at metaregression RAO incidence in the 5-Fr group was increasingly lower as the percentage of women included into the study increased (P = 0.02).Some potentially interesting technical details, such as sheath length, hydrophilic coating, or periprocedural anticoagulation, were not homogeneously reported in individual studies.Results of the present meta-analysis confirm the excellent safety profile of transradial procedures both with 5-Fr and 6-Fr system. A 5-Fr system could be preferred in patients with a higher bleeding propensity or kidney injury.