Postoperative clinical assessment in cases of tetralogy of Fallot can be very misleading. The persistence of right ventricular hypertrophy and a systolic ejection murmur may be incorrectly interpreted as evidence that relief of obstruction to the outflow tract of the right ventricle is inadequate. The disappearance of cyanosis is evidence that a right-to-left shunt through the ventricular septal defect has been corrected, but the presence of a pansystolic murmur in the fourth left interspace does not necessarily indicate that the defect has not been closed.