Cardiac troponins provide diagnostic and prognostic information on ischemic heart disease, but their roles in hypertrophic cardiomyopathy (HCM) are unclear. We sought to investigate the associations between elevated serum cardiac troponins T (cTnT) and I (cTnI) levels and cardiac injury in patients with HCM. We measured serum cTnT and cTnI in a peripheral vein of 73 consecutive HCM patients in stable condition. In addition, to examine the transcardiac release of cTnT and that of cTnI, we measured them in the aortic root and coronary sinus. Mitochondrial-and Ca2+-handling-related gene expression assays were analyzed by endomyocardial biopsy specimens. Based on the median value of serum cTnT, we divided the patients into two groups [group A: cTnT< 0.008 ng/mL,(n= 35), group B: cTnT group≥ 0.008 ng/mL,(n= 38)]. Left ventricular (LV) mass index was significantly higher, while LV ejection fraction was significantly lower, in group B than in group A. Meanwhile, there was a significantly positive correlation between the transcardiac gradient of serum cTnT or cTnI, and the mRNA level of troponin I3 (r= 0.473, r= 0.516, respectively). The mRNA level of troponin T2 significantly correlated with mRNA levels of sarco-endoplasmic reticulum Ca2+-ATPase 2, cytochrome c oxidase subunit 5B, and troponin I3 (r= 0.486, r= 0.957, r= 0.633, respectively). These findings indicate that both elevated serum cTnT and cTnI might be associated with cardiac dysfunction in patients with HCM, resulting from the impairment of mitochondrial function and Ca2+-handling protein.(Int Heart J 2013; 54: 202-206)