A 51-year-old woman was referred to our hospital with dyspnea. Chest roentgenogram on admission showed dilation of the pulmonary arteries and hyperlucency in the lung fields. An ultrasonic cardiographic examination showed that the right atrium and ventricle were dilated. Pulmonary thromboembolism due to left popliteal vein thrombosis was diagnosed by perfusion scintigram of the lung, which showed multiple wedge-shaped defects, and by digital subtraction angiogram, which showed a filing defect in the left popliteal vein. Antiphospholipid syndrome was diagnosed after IgG anticardiolipin antibody was defected. Scleroderma was subsequently diagnosed because the patient exhibited Raynaud's phenomenon and proximal scleroderma. Although closely associated with lupus erythematosus and other lupus variants, antiphospholipid syndrome has not been recognized as a common complication of scleroderma. This is the first report of a patient with pulmonary thromboembolism associated with antiphospholipid syndrome and scleroderma.