INTRODUCTION: The aim of the study was to compare the diagnostic accuracy of grayscale sonography and that of color Doppler imaging in the diagnosis of ovarian malignancy in a prospective study by the Sardinia-Navarra group. METHODS: The study was performed as a collaborative work at the 2 European university departments of obstetrics and gynecology between 1997 and 2007. A total of 2148 pelvic masses in 1997 women on whom transvaginal sonography were performed before surgical exploration were included in the study. An adnexal mass was first studied in grayscale sonography, and any cystic mass in which the echo architecture was not suggestive of benign tumor was categorized as malignant. Second, any solid excrescences or solid portions of the tumor were evaluated with color/power Doppler sonography. A mass was graded malignant if flow was shown within the excrescences or the solid areas and benign if there was no flow or if flow was only peripheral. RESULTS: Four hundred sixty-eight masses were malignant. Color Doppler evaluation was more accurate in the diagnosis of adnexal malignancies in comparison with grayscale sonography because of a significantly higher specificity (94% vs 89%, P = 0.001), with similar sensitivity (95% vs 98%, P = 0.44). The pretest probability of ovarian cancer was 22%, and this probability rose to 82% when the diagnosis was suggested by color Doppler evaluation. The diagnostic accuracy of the tests was also dependent on menopausal status. CONCLUSIONS: The evaluation of vessel distribution by color Doppler sonography in adnexal masses increases the diagnostic accuracy of grayscale sonography in the detection of adnexal malignancies in a large study population.