Etiology of deep vein thrombosis in ambulant patients (DVTA = TVPA in text) varies : cancer, blood disease, infectious focus, dysimmunity syndrome, dysglobulinemia, extrinsic compression, metabolic disorder, anomaly of hemostasis. A prospective study was carried out between June 1988 and September 1989 by angiologists in 5 regions of France to evaluate the diagnostic rentability of an epidemiologic survey and to determine possible distinctive characters of DVTA. The survey was comprised of a questionary, a full clinical examination and screening tests : chest xnray, abdominopelvic ultrasound imaging, a-uro/gynecologic examination, full blood count, serum iron, ferritin, uric acid, triglycerides, cholesterol, protein electrophoresis, antinuclear antibodies, circulating anticoagulant, hemostasis factors and liver function tests. The study included 128 patients, mean age 60 +/- 16 years with a DVTA developing without a previous immobilization. The usual predominance in the left leg was not observed. The etiology was identified in 33 cases, including 20 (15,6 %) as a result of the screening tests : anomalies of hemostasis (8), blood diseases (3), dysimmunity syndromes (4), extrinsic compression (3), cancer metastasis (1) and hypertriglyceridemia in a diabetic (1). The screening procedure was of no greater value in the absence of a triggering or predisposing factor, on the contrary. An anomaly of hemostasis was detected more frequently in the presence of local or regional triggering factors in the men (4 out of 4) and in the women on the pill (4 out of 4). The number of cancers discovered following screening (2 %) was smaller than that expected according to the literature (10 %). The risk of cancer following of DVTA remains to be demonstrated by the follow up in parallel of a group a DVTA and a control group. If curable localizations (colon and prostate) could be detected at an early stage after the diagnosis of a DVTA, the screening programme should be carried out.