Sixty-three patients who had undergone a BMT at age < or = 18 years were evaluated cross-sectionally to determine cardiac function as well as the long-term prevalence, types, severity, and risk factors of cardiac abnormalities. Patients were > or = 1 year post-BMT and were evaluated by history, resting ECG, echocardiography (ECHO), exercise treadmill test, chest X-ray, pulmonary function tests and review of past cardiac studies. Patients were assigned a New York Heart Association (NYHA) class based on an activity and cardiac symptoms questionnaire. Pretransplant preparative regimens included high-dose cyclophosphamide (CY) and total body/lymphoid irradiation (n = 38), CY in combination with other chemotherapy (n = 22), and other drug combinations (n = 3). Forty patients (63.5%) had received prior anthracyclines (median 307 mg/m2). Patients' ages ranged from 1.9 to 32 years (median 10.9 years) with median follow-up of 3.3 years (range 1-16.3 years). Twenty-six patients (41.3%) had a cardiac abnormality detected at follow-up. In 21 patients the abnormal finding had not been present at the pre-BMT evaluation. Ten patients (16.4%) had resting ECG abnormalities. Left ventricular ejection fraction (LVEF) by ECHO was mildly decreased to 50-54% in three patients and markedly decreased to 40% in one patient. Only one patient (1.7%) developed a mildly abnormal shortening fraction of 27%. All patients with ECHO abnormalities were asymptomatic. Twenty-three of 31 patients > or = 9 years of age (74%) who underwent a treadmill exercise test had a borderline or abnormal response to exercise. There was no correlation between demographic factors, previous therapy, preparative regimen or length of follow-up with the post-BMT ECG, ECHO and treadmill abnormalities. Overall, eight patients (12.7%) were symptomatic and NYHA class II or III, and all had abnormal exercise tests. The presence of symptoms and NYHA class were predictors for oxygen consumption during exercise (P = 0.03 and 0.02, respectively) and tended to predict overall treadmill results also. Late cardiac abnormalities do occur following BMT in childhood and thus, there is a clear need for continued, serial long-term cardiac evaluation in transplant survivors. Evaluations should include exercise stress testing to detect inadequate cardiac output as well as oxygen consumption during exercise.