Between 1919 and 1981, 16 children with primary cardiac tumors (8 rhabdomyomas, 5 fibromas, 2 myxomas, and 1 rhabdomyosarcoma) and 59 children with secondary tumors of the cardiovascular system were seen at The Hospital for Sick Children in Toronto. Distant metastases in 45 children of the latter group, in descending order of frequency, were from non-Hodgkin's lymphoma, neuroblastoma, soft tissue and bone sarcoma, Wilms' tumor, and hepatoma, and involved the myocardium and pericardium. In the remaining 14 children, tumor thrombi from Wilms' tumor (9 cases), adrenal (2 cases) and hepatocellular carcinoma (2 cases), and endodermal sinus tumor (1 case) extended directly into the great veins and/or cardiac chambers. Children with primary and secondary tumors often present with nonspecific clinical, plain radiographic, electrocardiographic, and M-mode echocardiographic findings. Early recognition, utilizing special diagnostic procedures such as two-dimensional echocardiography, computerized axial tomography, angiocardiography, and inferior venocavography, followed by elective surgical resection of tumor under cardiopulmonary bypass and/or radiation and chemotherapy, offers patients with cardiovascular tumors the best chance of cure.