In Behçet’s disease, deep venous thrombosis occurs primarily in the lower extremities. Total recanalization rate is low, so thrombotic segment could be detected by imaging afterward. For disclosing vein involvement, leg swelling is commonly queried in the history taking in those patients. However, there are no data about the presence of “silent” thrombosis in patients with BD. We aimed at investigating the integrity of venous vessels in BD, without any known vascular event by using Doppler ultrasonography (DU). Patients having past events revealed in the vascular questionnaire or physical findings attributable to vascular disease were excluded. Various degree of venous insufficiency was detected in 74 patients in BD (74%), 24 out of 33 patients (72%) in AS and in 8 out of 34 (25%) in HC group. All were at the lower extremities, and there is no difference in the frequency between BD and AS, while both were significantly higher than in HC (P = 0.001, and 0.004, respectively). Six patients with BD (6%) have chronic venous thrombi at the lower extremities and none in either AS and HC. As a non-invasive method, DU of lower extremities may disclose “silent” thrombosis. Venous insufficiency in those patients should be considered cautiously as an indicator of vein involvement.