Extremely low-birth-weight (ELBW) infants frequently manifest signs of cardiac dysfunction requiring inotropic support. It is not clear if this is due to cardiac injury, which can be monitored by measuring cardiac troponin T (cTnT). We performed a nested prospective cohort study at a university level III neonatal intensive care unit. The study included 27 infants weighing between 500 and 999 g. Exclusion criteria included evidence of sepsis, use of postnatal steroids, and cardiac anomalies. Measurements included serum cTnT and echocardiogram in the first 48 hours of life. The mean serum cTnT level of the study population was 0.52 ± 0.38 ng/ml. It was higher in those with lower Apgar scores (0.89 ± 0.37 if 5-minute Apgar < 4 vs 0.36 ± 0.26 ng/ml, p < 0.001) and correlated to initial base deficit (r = -0.37, p < 0.05). Infants who required inotropic support had higher cTnT levels than those who did not (0.73 ± 0.43 vs 0.39 ± 0.29 ng/ml, p < 0.03). cTnT concentrations did not relate to simultaneous echocardiographic measures of cardiac function. In ELBW infants, serum cTnT levels are higher than normally seen in term infants and adults, and they are higher in infants with greater perinatal stress as well as those who show evidence of cardiac dysfunction requiring pressor support.