Although malignant melanoma has a great propensity (38-50%) for cardiac involvement, as indicated by autopsy findings, cardiac metastases are rarely identified ante-mortem. The aim of this study was to record abnormal electrocardiographic and echocardiographic findings in patients with malignant melanoma. One hundred and eighty-five consecutive patients (male/female, 99/86; mean age, 59.6 years) with histologically proven malignant melanoma (American Joint Committee on Cancer stages II-IV), and with no known history of heart disease, were evaluated prospectively over a period of 11 years. The cardiologic findings considered were an unexpected delayed conduction of an electrical stimulus, recorded by high-resolution signal-averaged electrocardiogram (presence of ventricular late potentials), prolongation of the PR, QRS and QTc segments in a surface electrocardiogram, and abnormal Q waves. Echocardiographic findings comprised pericardial implantation/effusion or presence of intracavitary/intramyocardial metastases. Forty-one abnormal findings were recorded, pertaining to 38 of the 185 patients (19.5%). In particular, PR interval prolongation was found in eight patients (4.3%) and QTc interval prolongation in 11 (6%). Abnormal Q waves were recorded in five patients (2.7%). The filtered QRS interval was prolonged in seven patients (3.8%). Finally, echocardiographic examination showed discrete pericardial implantations and small to moderate pericardial effusion in six patients (3.2%) and intracavitary/intramyocardial metastases in four (2.1%). The median survival of these patients was 33 months (95% confidence interval, 19.9-46.1 months). It can be concluded that abnormal electrocardiographic and echocardiographic findings are recorded at the time of diagnosis of the disease in a significant percentage of patients with malignant melanoma.