A 48-year-old woman presented with abdominal fullness and a palpable "mass" in the left lower quadrant. Ultrasonography showed a large, rounded, hypoechoic mass. Contrast-enhanced helical CT of the abdomen demonstrated a well-circumscribed, heterogeneously but vividly enhancing mass. The uterus had a leiomyomatous configuration on CT. Uterus and mass revealed the same enhancing pattern. Thin section CT revealed a long, thin stalk connecting the mass with the body of the uterus. Surgical removal of both uterus and the mass confirmed the diagnosis of a pedunculated subserosal leiomyoma originating from a leiomyomatous uterus.