The aim of this study was to evaluate over one year the minimal etiologic screening carried out on each patient hospitalized in Internal Medicine for a deep venous thrombosis (DVT) and to search for clinical features possibly relating thrombosis to neoplasia. 53 patients (27 male and 26 female; mean age 63.6 years, range: 18-19) with DVT of the lower limbs were included in the study. The initial etiologic screening consisted of a complete clinical examination, a biological assessment (blood cell and platelet count, Activated Partial Thromboplastin Time, inflammation and liver investigations), a radiography of the thorax and abdomino-pelvic ultrasonography. This etiologic screening was evaluated one year after the thrombotic event. The initial assessment was positive in 44 cases (83% of the patients), 9 thrombosis remained unexplained. Neoplasia was identified in 8 cases (15% of the patients), the diagnosis being often evoked at the time of interrogation or during the clinical examination; the systematic biological assessment only revealed an etiology in one case: this was a primary thrombocythemia discovered by platelet count. On evaluation one year later, amount the 9 DVT unexplained by the initial screening, 8 remained totally unexplained. On the other hand, a cancer of the colon revealed by proctorrhagia during oral anticoagulant treatment, had been undiscovered. No significant difference was found between the two groups (cancers and noncancerous etiologies) as concerns age, sex, thrombus topography, the side affected or the embolic events. However, the occurrence of subsequent thrombosis under well controlled anticoagulant treatment clearly characterises thrombosis associated with neoplasia.(ABSTRACT TRUNCATED AT 250 WORDS)