From April 1, 1980, through March 31, 1998, 51 consecutive patients were hospitalized in our department for primary UEDVT. None of these patients had a history of drug abuse or recent venous injections, central venous catheterization, pacemakers, major trauma, cancers, or heart failure, or evidence of liver or kidney disease. Of these patients, 21 were men and 30 were women, with a median age of 32 years (age range, 15-86 years). All but 2 patients (1 from the West Indies, 1 from Réunion) were from Europe. A total of 55 UEDVTs occurred in these 51 patients. Two patients had bilateral axillary-subclavian vein thromboses diagnosed at the first examination, 1 patient had a contralateral recurrence 2 years after the first event, and 1 patient had an ipsilateral recurrence 9 months after the first event. The diagnosis was confirmed by duplex ultrasonography in 23 cases and by phlebography in 32 cases. Phlebographic examination was performed when the ultrasonographic diagnosis was not definite (eg, when compressibility of the vein was not evaluable at the subclavian level) or when the head of the thrombus was not seen. The thrombi involved the axillary and/or subclavian veins in 54 cases, the brachial vein in 10 cases, the brachiocephalic trunk in 12 cases, the internal jugular vein in 3 cases, and the superior vena cava in 1 case. Screening for pulmonary embolism by lung scan, pulmonary angiography, or helicoidal computed tomography was performed in 26 cases, and results were positive in 11 (20%) of the 55 thromboses.