Adnexal masses can have gynecologic or nongynecologic etiologies, ranging from normal luteal cysts to ovarian cancer to bowel abscesses. Women who report abdominal or pelvic pain, increased abdominal size or bloating, difficulty eating, or rapid satiety that occurs more than 12 times per month in less than a year should be evaluated for ovarian cancer. Pelvic examination has low sensitivity for detecting an adnexal mass; negative pelvic examination findings in a symptomatic woman should not deter further workup. Ectopic pregnancy must be ruled out in women of reproductive age. A cancer antigen 125 (CA 125) test may assist in the evaluation of an adnexal mass in appropriate patients. CA 125 levels are elevated in conditions other than ovarian cancer. Because substantial overlap in CA 125 levels between pre- and postmenopausal women may occur, this level alone is not recommended for differentiating between a benign and a malignant adnexal mass. Transvaginal ultrasonography is the first choice for imaging of an adnexal mass. Large mass size, complexity, projections, septation, irregularity, or bilaterality may indicate cancer. If disease is suspected outside of the ovary, computed tomography may be indicated; magnetic resonance imaging may better show malignant characteristics in the ovary. Serial ultrasonography and periodic measurement of CA 125 levels may help in differentiating between benign or potentially malignant adnexal masses. If an adnexal mass larger than 6 cm is found on ultrasonography, or if findings persist longer than 12 weeks, referral to a gynecologist or gynecologic oncologist is indicated.