Patients with cyanotic congenital heart disease exhibit an increased incidence of thrombotic episodes and are frequently thrombocytopenic. We studied the sera of 15 patients with this type of heart malformation, searching for anticardiolipin antibodies. 3/15 had positive results. The three of them were adult females; two had thrombotic episodes and a false positive VDRL. Thus, cyanotic congenital heart disease may be another disease entity associated with the antiphospholipid syndrome.