Purpose : To evaluete the sonographic features of ovarian mass torsion. Materials and Methods : We evaluated the sonographic findings in 22 cases of torsion cystic ovarian mass, benign teratoma(n=21), and normal ovary (n=1) confirmed surgically on pathologically. We classified the ovarian mass into two groups as sonographic ally cystic (n=15) or non-cystic mass(n=6). The patients were 17-72 years old(mean : 36.9). We retrospectively reviewed US examination with respect to (1) free fluid in Douglas pouch, (2)pelvic mass & mass wall thickening, (3)dilateduterine tube, (4)prominent follicles, (5) engorged vessels, and (6)beak-like echo in torsion site. The combined conditions of torsion were uterine myoma(n=1) and intrauterine pregnancy(n=3) Results : In sonogram, sonographiccystic mass (n=15) group showed (1)free fluid in Douglas pouch (9/15), (2)mass wall thickening(6/15), (3)dilated uterine tube(2/15), and sonographic non-cystic mass(n=6) group showed (1) free fluid in Douglas pouch (3/6). Insonogram, torsion of the normal ovary(n=1) showed (1) free fluid in Douglas pouch, and (2) prominent follicles. Conclusion : If sonogram of reproductive aged women with acute abdomen showed free fluid in Douglas pouch and pelvic mass with wall thickening, ovarian mass torsion is suggested. But clinical features of acute abdomen and clinical diagnosis of torsion are more important than sonographic features.