We here describe a young patient who presented with chronic Budd-Chiari syndrome. An exhaustive etiological investigation to detect a procoagulable state was negative except for factor V mutation (factor V Leiden), a factor associated with resistance to activated protein C. Factor V Leiden is known to be a common, high risk factor for thrombosis. This factor should be routinely investigated in patients with Budd-Chiari syndrome, as factor V Leiden mutation is probably the procoagulable state responsible for many cases of "idiopathic" Budd-Chiari syndrome.