Five patients with isolated superior mesenteric vein thrombosis were diagnosed by ultrasonography (US) and computed tomography (CT). The presence of echogenic material within the venous lumen was identified in all patients on sonography. A significant venous enlargement was sonographically observed in 1 patient with tumoral thrombosis. A sharply defined vascular wall with a rim of increased density and a central area of low attenuation was observed in 3 of 5 patients on CT. None of our patients developed bowel infarction secondary to venous occlusion and a conservative management was established in all.