PURPOSE: To evaluate the usefulness of the 'bridging vessel sign'in differentiating uterine sub-serosal leiomyoma from other pelvic masses mimicking leiomyoma on color Doppler ultra sound. MATERIALS and METHODS: Histologically (n=58) and clinically (n=1) proven 59 masses from 55 women were included in this study. Histologic diagnoses included leiomyoma (n=32) and various kinds of other pelvic masses (n=27). On gray scale ultrasound, the size of tumor and presence of the ovaries were recorded. On color Doppler ultrasound, the presence of 'bridging vessel sign', which was defined as a linear vessel demonstrated between the mass and the uterus was documented. Uterine subserosal leiomyoma was diagnosed on the basis of finding this sign, and the diagnostic accuracy of this sign in differentiating subserosal leiomyoma from other pelvic tumors was calculated. In addition, the diagnostic accuracy of this sign combined with the visibility of theopsilateral ovary was compared. RESULTS: The size of subserosal leimyomas ranged from 4.2 to 22.1 cm (mean, 8.3 cm) while the size of other pelvic masees, from 4.6 to 21.5 cm (mean, 9.6 cm). The 'bridging vessel sign' was demonstrated in thirty of 32 leiomyomas and in three of 27 other pelvis masses. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of the 'bridging vessel sign' in the diagnosis of subserosal leiomyoma were 93.8%, 88.9%, 91.5%, 90.9% and 92.3%, respectively. The detection of the ipsilateral ovary was possible in 14 of 30 women with leiomyomas and in four of 25 women with other pelvic masses. The sensitivity, specificity, accuracy, positive predictive value and negative predictive value of this finding in the diagnosis of subserosal leiomyoma were 46.7%, 84.0%, 63.6%, 77.8%, and 56.8%, respectively. CONCLUSION: 'Bridging vessel sign' can be an useful finding in the differential diagnosis of subserosal leiomyomas from other pelvic masses mimicking leiomyoma.