BACKGROUND: The incidence of deep venous thrombosis is 0.6/1000 habitants and when symptomatic its diagnosis by duplex scan has 100% sensitivity and 98% specificity. OBJECTIVES: The aim of this study was to evaluate the findings of the duplex scan in patients with clinical suspicion of deep venous thrombosis. METHODS: 239 consecutive outpatients (59.2 +/- 18.6 years, 164 female) were evaluated by duplex scan. RESULTS: According to symptoms 101 (42.3%) were related to the right lower limb; 113 (47.3%) to the left lower limb; and 25 were related to both lower limbs. Forty-eight patients presented a normal duplex scan. Venous thrombosis was found in 117 patients (0.49; CI 0.43-0.55): 75 with deep venous thrombosis (DVT), 22 with superficial venous thrombosis (SVT) and 20 with both DVT and SVT. Other pathologies were found in 74 patients. Among patients with DVT the most involved veins were below the knee. Among patients with SVT, 20 (47.6%) showed progression to the deep venous system: 9 (45%) by perforans veins; in 6 by saphenous-femoral junction (30%); and in 5 (25%) by saphenous-popliteal junction. CONCLUSION: Deep venous and superficial venous thromboses were diagnosed in 49% of cases. In 30.9% of cases, the duplex scan indicated other pathologies.