Behçet's disease (BD) is a multisystemic disease of unknown aetiology characterized by chronic relapsing oral aphthous lesions, genital ulcers, uveitis, and vasculopathy of both arteries and veins of all sizes. We present the case of a female patient, with BD on oral contraceptive pills, who sustained deep venous thrombosis of the long saphenous vein. The patient was found to be a carrier of a homozygous mutation of the prothrombin (factor II) G20210A gene. Our case suggests that a thrombophilia work-up may be warranted in BD patients, especially young women before they are prescribed oral contraceptives.