Venous aneurysms are a rare pathology. The possible complications are rupture, thrombosis and subsequently pulmonary embolism. The case of a 54-year-old male is reported, who was admitted on the suspicion of pulmonary embolism to our department. This suspicion was confirmed by scintigraphy and computed tomography. Further examination by colour coded duplex sonography showed an aneurysm of the popliteal vein in clinically asymptomatic legs, as a possible cause of the pulmonary embolism. The finding was confirmed phlebographically. After successful surgical treatment of the aneurysm the patient got an anticoagulation therapy for 6 months. In the case of thromboembolism the entire venous system can be affected. Therefore an examination of the peripheral veins should be carried out whenever there is an occurrence of pulmonary embolism.