Congenital subclavian steal may result from various anomalies of the aortic arch. The most common predisposing type is the right aortic arch with an isolated left subclavian artery arising from a left ductus arteriosus. A rare variant includes isolation of the left common carotid as well as the left subclavian arteries. The case of an infant with polysplenia--F-anisosplenia syndrome and this rare variant of congenital left subclavian steal is presented. This anomalous constellation has been heretofore unreported and illustrates a new situs abnormality that may complicate the polysplenia syndrome.