We review and emphasize the importance of gynecologic ultrasound scan for the preoperative evaluation of adnexal masses. Transvaginal ultrasound performed by a trained clinician has a good sensitivity and specificity for discriminating benign and malignant adnexal masses. In conjunction with a carefully obtained history, assessment of risk factors, a focused physical examination and serum markers, the information obtained by a gynecologic ultrasound evaluation can assist the clinician in the diagnosis and treatment of adnexal masses.