BACKGROUND: The Budd-Chiari syndrome (BCS) is hepatic venous outflow obstruction. What is known about the syndrome is based on small studies of prevalent cases. OBJECTIVE: To characterize the causes and treatment of incident BCS. DESIGN: Consecutive case series of patients with incident BCS, enrolled from October 2003 to October 2005 and followed until May 2006. SETTING: Academic and nonacademic hospitals in France, Spain, Italy, Great Britain, Germany, Belgium, the Netherlands, Portugal, and Switzerland. PATIENTS: Persons older than 16 years with definite hepatic outflow obstruction diagnosed by imaging. Persons with hepatic outflow obstruction due to heart failure, sinusoidal obstruction syndrome, cancer, or liver transplantation were excluded. MEASUREMENTS: Signs and symptoms; laboratory and imaging findings; diagnosis; treatment; and overall, transplantation-free, and intervention-free survival. RESULTS: 163 incident cases of BCS were identified. Median follow-up was 17 months (range, 0.1 to 31 months). Most patients (84%) had at least 1 thrombotic risk factor, and many (46%) had more than 1; the most common was myeloproliferative disorders (49% of 103 tested patients). Patients were mainly treated with anticoagulation (140 patients [86%]), transjugular intrahepatic portosystemic shunting (56 patients [34%]), or liver transplantation (20 patients [12%]), and 80 patients (49%) were managed noninvasively. Only 3 patients underwent surgical shunting. The survival rate was 87% (95% CI, 82% to 93%) at 1 year and 82% (CI, 75% to 88%) at 2 years. LIMITATION: Treatment was not standardized across all centers, and data on important clinical variables were missing for some patients. CONCLUSION: Most patients with BCS have at least 1 thrombotic risk factor, and many have more than 1; myeloproliferative disorders are most common. One- and 2-year survival rates are good with contemporary management, which includes noninvasive therapies (anticoagulation and diuretics) and invasive techniques. Transjugular intrahepatic portosystemic shunting seems to have replaced surgical shunting as the most common invasive therapeutic procedure. PRIMARY FUNDING SOURCE: Fifth Framework Programme of the European Commission.