Audit of and feedback on both group and individual data provided immediately after the point of care and compared with realistic benchmarks of excellence have been demonstrated to drive change. This study sought to evaluate the impact of immediate benchmarked quantitative case-based performance feedback on the clinical practice of cardiologists practicing at a private hospital in Brisbane, Australia. The participating cardiologists were assigned to one of two groups: Group 1 received patient and procedural details for review and Group 2 received Group 1 data plus detailed radiation data relating to the procedures and comparative benchmarks. In Group 2, Linear-by-Linear Association analysis suggests a link between change in radiation use and initial radiation dose category (p=0.014) with only those initially 'challenged' by the benchmarks showing improvement. Those not 'challenged' by the benchmarks deteriorated in performance compared with those starting well below the benchmarks showing greatest increase in radiation use. Conversely, those blinded to their radiation use (Group 1) showed general improvement in radiation use throughout the study compared with those performing initially close to the benchmarks showing greatest improvement. This study shows that use of non-challenging benchmarks in case-based radiation risk feedback does not promote a reduction in radiation use; indeed, it may contribute to increased doses. Paradoxically, cardiologists who are aware of performance monitoring but blinded to individual case data appear to maintain, if not reduce, their radiation use.