In order to evaluate physicians' willingness to seek legal action to mandate surgery when parents refuse surgery for various congenital heart lesions, we surveyed pediatric cardiologists and cardiovascular surgeons at 4 children's hospitals. We asked whether physicians would support parental refusal of surgery for specific heart defects and, if not, whether they would seek legal action to mandate surgery. We then analyzed associations between physicians' willingness to mandate surgery and national operative mortality rates for each lesion. We surveyed 126 cardiologists and 9 cardiac surgeons at four tertiary referral centers. Overall response rate was 77%. Greater than 70% of physicians would seek legal action and mandate surgery for the following lesions: ventricular septal defect, coarctation of the aorta, complete atrioventricular canal, transposition of the great arteries, tetralogy of Fallot, and unobstructed total anomalous pulmonary venous return. Surgery for all of these lesions has reported mortality rates of < 5%. Physicians were less likely to seek legal action when parents refused surgery for Shone complex, any single ventricle lesion, or any congenital heart disease accompanied by Trisomy 13 or Trisomy 18. Among experts in pediatric cardiology, there is widespread agreement about the appropriate response to parental refusal of surgery for most congenital heart lesions, and these lesions tended to be heart defects with lower surgical mortality rates. Lesions for which there was greater consensus among experts were those with the best outcomes. There was less consensus for lesions with higher mortality rates. Such surveys, revealing disagreement among expert professionals, can provide an operational definition of the current professional "gray zone" in which parental preferences should determine treatment.