Several authors have reported an association between neuroblastoma and congenital heart disease; others contend that, unlike specific well-known associations between malignancy and congenital defects (Wilm's tumor and aniridia, leukemia and Down's syndrome), no real relationship exists. We present three cases of cyanotic congenital heart disease in which subclinical neuroblastoma was found. We speculate that abnormal neural crest cell migration and development may be a common link between cardiac malformations and congenital neuroblastoma.