TRICUSPID ATRESIA is a rare but severely life-limiting malformation of the heart. We recently reported a series of 101 patients from the Children's Hospital Medical Center, Boston, Mass., in which survival to 17 years of age with palliative surgery was 50%.' Early survival was related to the success of surgical intervention and adequacy of pulmonary blood flow. There was an increase in mortality beginning in the middle of the second decade; two-thirds of patients alive at age 15 died by age 23. Causes for the late mortality in this group could be related to the state of the myocardium since only two patients beyond two years of age, free of congestive heart failure, died at operation. Long-term survivors have been noted to have normal to increased pulmonary blood flow and frequently exhibit congestive failure.2 3 To investigate the role of left ventricular function in the survival of patients with The 28 patients were classified into their radiologic group according to appearance of the pulmonary vascularity, as previously reported." 4 Twenty-one group A patients had decreased pulmonary vascularity prior to surgical palliation. Volume studies were available prior to surgery in ten patients, after surgery in nine patients, and both before and after surgery in three patients. Six patients had normal or increased pulmonary vascularity (group B) and did not require shunt surgery. The radiologic appearance of the pulmonary vascularity was a reasonable estimate of pulmonary blood flow since both the mean Qp/Q8 and systemic saturation were significantly different between the two unoperated groups (13 group A and six group B patients, P < 0.02, and P < 0.001 respectively).