This paper presents a case of omental torsion with necrosis which might be caused by inguinal hernia. A 62-year-old man was admitted to the hospital because of left inguinal bulging, left scrotum swelling and right lower abdominal pain. He had a sudden on set of urgent high fever as 38°C. On physical examination, tenderness and muscle defense were noted in the right lower abdomen. Computed tomography (CT) of the lower abdomen demonstrated a marked mass with concentric folds or an arrow pattern, and omental torsion with necrosis was suspected. On emergency laparotomy, most of the greater omentum was twisting and revealed hemorrhagic necrosis. The necrotic omentum with normal margin was resected and a repair of the left hernia was made. No malignancy was revealed pathologically. Postoperative course was uneventful. We reviewed 98 cases seen in the Japanese literature, including this case and present some notes about the disease. Without the knowledge of this disease, it is difficult to diagnose preoperatively in that. CT is helpful. No death have been reported.