Objective: Initial treatment in the management of acute mesenteric vein thrombosis (MVT) is controversial. Some authors have proposed a surgical approach, whereas others have advocated medical therapy (anticoagulation). In this study, we analyzed and compared the results obtained with surgical and medical treatment to determine the best initial management for this disease. Methods: We retrospectively reviewed the records of patients treated for MVT in a secondary care surgical department from January 1987 to December 1999. Before January 1995, our departmental policy was to perform surgery in patients with suspected MVT. Since January 1995, we have preferred a medical approach when achievable. Each patient in this study was assessed for diagnosis, initial management (laparotomy or anticoagulation), morbidity, mortality, duration of hospitalization, the need for secondary operation, portal hypertension, and survival rates. Results: Twenty-six patients were treated, 14 before January 1995 (group 1) and 12 since January 1995 (group 2). Morbidity, mortality, secondary operation, portal hypertension, and 2-year survival rates were 34.6%, 19.2%, 15.3%, 19.2%, and 76.9%, respectively. No statistical difference was observed between the two groups. The mean duration of hospitalization was 51.6 days in group 1 and 23.2 days in group 2 (P <.05). Among the 12 patients treated by means of laparotomy with bowel resection, 10 patients (83%) had mucosal necrosis without transmural necrosis at pathologic study. Conclusion: Nonoperative management for acute MVT is feasible when the initial diagnosis with a computed tomography scan is certain and when the bowel infarction has not led to transmural necrosis and bowel perforation. The morbidity, mortality, and survival rates are similar in cases of surgical and nonoperative management. The length of hospital stay is shorter when patients are treated with a nonoperative approach. A nonoperative approach, when indicated, avoids the resection of macroscopically infarcted small bowel (without transmural necrosis) in cases that are potentially reversible with anticoagulation alone. (J Vasc Surg 2001;34:673-9.)