Background: Treatment of splanchnic vein thrombosis (SVT) is a clinical challenge due to heterogeneity of clinical presentations, increased bleeding risk and lack of evidences from clinical trials. We carried out an international registry aimed to describe current treatment strategies and factors associated with therapeutic decisions in a large prospective cohort of SVT patients. Methods: Between May 2008 and January 2012, consecutive SVT patients were enrolled in the registry and information on clinical presentation, risk factors, and therapeutic strategies was collected in an electronic database. Clinical outcomes during the first month of treatment were documented. A two-year follow up is ongoing. Results: 613 patients from 12 countries were enrolled in the registry. Mean age was 53.1 (SD ± 14.8) years (range 16-85); 62.6% were males, 74.4% Caucasians. SVT occurred in the portal vein in 470 patients, in the mesenteric vein in 266, in the splenic vein in 139, and in the supra-hepatic veins in 56; 38.8% of patients had multiple vein segments involved. In 29.8% of patients SVT diagnosis was incidental. Most common risk factors included cirrhosis (27.8%), solid cancer (22.3%), intra-abdominal inflammation/infection (11.5%), surgery (8.9%), and myeloproliferative neoplasm (MPN)(8.2%); in 27.6% of patients SVT was idiopathic. During the acute phase, 471 (76.8%) patients were treated with anticoagulant drugs: unfractionated heparin (10.4%), low molecular weight heparin or fondaparinux (66.4%), vitamin K antagonists (VKA) (48.5%). Four patients received aspirin, 9 received thrombolysis. A total of 135 patients (22.0%) remained untreated. Of patients with incidentally diagnosed SVT, 61.1% received anticoagulant treatment. Incidental diagnosis (p