Early detection of damage to cardiac myocytes after cardiotoxic chemotherapy in paediatric patients may allow timely preventive measures to be taken. We investigated the diagnostic value of cardiac troponin T (cTnT) after the administration of cardiotoxic chemotherapy. In 38 children, cTnT levels were measured at three time points during the first 24 h after 58 cardiotoxic chemotherapy cycles (163 samples). An abnormal cTnT level, defined as a cTnT>0.010 ng/ml, was measured in only six samples from 3 patients. After completion of chemotherapy, 7 out of the 38 patients had left ventricular dysfunction (LV dysfunction). Only 1 of these 7 patients had an elevated cTnT level. 2 other patients with elevated cTnT levels did not develop LV dysfunction until 2 and 7 months after the cTnT measurement. Our data show that the measurement of cTnT within 24 h after administration of chemotherapy does not have a high sensitivity for the identification of patients with subsequent subclinical cardiotoxicity.