Cardiac troponin I (cTnI) is a sensitive and specific marker of myocardial injury. The degree of myocardial injury associated with pediatric cardiac catheterization is unknown. We sought to investigate cTnI after pediatric cardiac catheterization, and to evaluate the degree of elevation observed with specific types of interventions. Seventy-three pediatric catheterizations were evaluated. Diagnostic procedures and interventions not expected to cause myocardial injury were assigned to group I, whereas interventional procedures expected to be associated with cardiac injury were assigned to group II. Group II procedures were further subdivided based on type of intervention. Serum samples were obtained before and after all procedures and analyzed for cTnI. Postprocedure cTnI levels were compared across groups and correlated with age and weight. Procedures in group II were associated with significantly higher cTnI levels than group I (median 2.65 ng/ml; interquartile range 0.9 to 4.9 ng/ml for group II vs 0.3; 0.3 to 1.6 ng/ml for group I, p <0.001). Within group II, cTnI was inversely correlated with age (p <0.05) and weight (p <0.05). Radiofrequency catheter ablation (RFA) caused higher cTnI levels than other types of interventions (median 3.7 ng/ml; 1.9 to 9.5 ng/ml for RFA vs 1.75; 0.7 to 4.9 ng/ml for non-RFA, p <0.05). Most pediatric interventional catheterization procedures are associated with myocardial injury, as evidenced by elevation of cTnI, with RFA causing higher levels than other interventions. Conversely, most diagnostic procedures are associated with no detectable myocardial injury. When compared with adult studies, pediatric patients seem to be at higher risk for myocardial injury from interventional cardiac catheterization.