BACKGROUND Plasma troponin is a risk factor for cardiac events in various populations. We evaluated the determinants and predictive value of plasma cardiac troponin I (cTnI) during the long-term follow-up of heart transplantation. RESULTS We prospectively measured cTnI in 100 heart transplant recipients, 13.0 ± 6.0 years after transplantation, during a routine visit including echocardiography and laboratory measurements. The patients were followed for 21.3 ± 4.9 months after this troponin measurement. cTnI ≥0.006 μg/L (detection threshold) was found in 37 of these 100 patients. Plasma troponin significantly increased with the presence and severity of coronary lesions detected by means of coronary angiography and was significantly associated with age, left ventricular mass, history of post-transplantation heart failure, body mass index, and plasma creatinine. Of 37 patients with cTnI ≥0.006 μg/L, 13 had a cardiac event during follow-up compared with 2 of 63 patients with cTnI <0.006 μg/L (P < .0001). The relation between cTnI and cardiac events remained significant in multivariate analysis. CONCLUSIONS cTnI is frequently detectable during long-term follow-up after heart transplantation and is associated with chronic graft rejection and renal failure. A detectable cTnI may help identify heart transplant recipients at high risk of cardiac events.