Abstract Background Vascular thrombosis in Behçet syndrome (BS) is frequent and associated with high morbidity and mortality rates. Purpose To investigate BS patients presenting with a thrombotic event (TE) and identify the factors associated with relapse. Methods We retrospectively conducted a single-center, descriptive, and analytic study, from 2000 to 2022, enrolling all BS patients presenting TE, including venous thrombosis (VT) and/or arterial thrombosis (AT). Results TE was observed in 136/531 patients (25%), mostly men (83%), aged 29 ± 9 years (11-50) at BS onset. TE was the initial presentation of BS (32%) or occurred after a median of 4 years [0;25]. It included VT (92.5%), AT (18%), and both (13%). VT mostly consisted of DVT in the lower extremities (60%), vena cava (30%), and cerebral (15%) veins. It involved one (55%), two (27%), and multiple (16%) veins (Figure 1). AT mainly affected the pulmonary (42%), femoral (21%), coronary (17%), cerebral (8%) arteries, and aorta (8%). Arterial aneurysms were common (18%), especially in the pulmonary arteries (11%). Intracardiac thrombosis was also visualized (10%). Noncardiovascular manifestations mainly included aphthous ulcers (96%), pseudofolliculitis (36%), ocular lesions (41%), and arthralgias (22%). Hemostasis parameters were within normal ranges. Patients were treated with colchicine (98%), corticoids (98%), and immunosuppressants (80%). Anticoagulation and anti-platelet aggregation were administered in 90% and 15% of the cases, respectively. Six patients underwent vascular surgery. Post-thrombotic syndrome was noted in 14% of the patients. Relapse was common (25%), mainly occurring in men (81%), of younger age (24 ± 6) at first TE. Relapse consisted of one (55%), two (32%), or multiple episodes (13%). It occurred in the same vascular system initially affected (69%), a different one (12%), and both at the same time (19%). Multivariable analysis revealed TE at onset (OR= 2.99, 95% CI[1.14 ; 7.82], p=0.02), arterial thrombosis (OR= 2.91, 95% CI[1.10 ; 8.40], p=0.04), and arterial aneurysms (OR= 2.58, 95% CI [1.09 ; 8.45], p=0.02) as factors significantly associated with TE relapse (Figure 2). Conclusion Our study highlights several particularities of TE in BS, with TE at onset, arterial thrombosis, and arterial aneurysms emerging as significant relapse factors.