A remarkable patient is described, a child who has survived until the age of 7 years with hypoplastic left heart syndrome (mitral and aortic atresia) without surgical intervention. The child has led an active, normal life and, aside from minimal cyanosis, has remained asymptomatic. The unique clinical course for this patient is the result of a number of favorable hemodynamic factors that have not been previously reported in an individual patient with hypoplastic left heart syndrome and intact ventricular septum widely patent ductus arteriosus, adequate retrograde coronary flow, unrestricted pulmonary venous return, and absence of significant vascular obstructive disease. This documentation of long-term survival in a child without surgical treatment for mitral and aortic atresia suggests that successful early palliative treatment for infants with this syndrome could also result in a favorable prognosis.