Small bowel volvulus is usually secondary to conditions such as malrotation, congenital bands, postoperative adhesions, and internal hernias. Primary small bowel volvulus in an adult is rare, and only 14 cases had been reported in Japan as of 1994. Preoperative diagnosis is difficult, because clinical examinations and plain films are of limited diagnostic value. In our cases, CT showed signs of small bowel volvulus such as a U-shaped configuration or radial distribution of distended and fluid-filled loops of the small bowel converging toward the point of torsion, tightly twisted mesentery around the point of torsion (whirl sign), fusiform tapering loop (triangular sign in the cross section or beak sign in the longitudinal section), and signs of bowel ischemia or infarct such as attached mesenteric fluid and blurred mesenteric folds. CT enabled us to diagnose not only small bowel volvulus but also bowel ischemia or infarct.