Objective. We investigated the usefulness of serum cardiac Troponin T (cTnT) to detect doxorubicin related cardiotoxicity as a non- invasive and reliable method. Patients and Methods. Twenty-four patients who received doxorubicin for their solid tumors at cumulative doses of 400 mg/m(2) or higher, between June 1982 and August 2000, were included in this study. None of them had clinical signs or symptoms of cardiotoxicity. The age range was 3-31 years (median 14), and male to female ratio was 14/10. The systolic and diastolic cardiac functions were evaluated by two-dimensional, M-mode, and Doppler echocardiography. Serum cTnT levels were measured by a third generation immunoassay method and the lowest detectable level was 0.010 ng/ml. Results. The cumulative doxorubicin doses were at the range of 400 and 840 mg/m(2) (median 480). The time past from the last doxorubicin dose was 1-168 months (median 12). All of the patients had normal chest X-rays, electrocardiograms, and nine patients (37.5%) had abnormal systolic or diastolic cardiac function parameters. The median cumulative doxorubicin doses of the patients with normal and abnormal echocardiographic parameters were 480 and 440 mg/m(2), respectively. Serum cTnT values of 21 patients were below the detection limit (< 0.010 ng/ml). There was no statistical difference between serum cTnT levels of the patients with normal and abnormal echocardiographic findings (P=0.376). Conclusions. No correlation was found between serum cTnT values, cumulative doxorubicin doses, and systolic or diastolic cardiac functions. We can conclude that echocardiographic follow-up is more reliable than serum cTnT levels for detecting subclinical cardiac toxicity. (C) 2003 Wiley-Liss, Inc.