Gynecologists have to differentiate between benign and malignant adnexal masses. We review the evidence supporting to the specialty care of a gynecologic oncologist on the basis of the physical examination, imaging studies, family history, and CA 125 determination. We recommend adherence to the ACOG/SGO Joint Opinion guidelines. Specifically, referral to a gynecologic oncologist seems warranted for postmenopausal women with elevated CA 125, nodular or fixed pelvic mass, metastatic disease, ascites, or family history of breast or ovarian cancer. Premenopausal women should be referred if the CA 125 is elevated above 200 U/mL, there is an evidence of metastatic disease or ascites, or strong family history of breast or ovarian cancer.