Background: The occurrence of fallopian-tube torsion as well as bilateral adnexal masses are rare in adolescents. Case: A 13-year-old girl who had attained menarche 6 months previously, complained of back pain of 7 months' duration and lower abdominal pain of 1 month's duration. Findings from her general and other systemic examinations were normal. Her hymen was intact, and rectal examination revealed a tender mass of 5 · 6 cm, which was felt anterior to the rectum. Transabdominal sonography showed bilateral adnexal masses, of which the left one was a complex echogenic mass of 7.43 · 5.41 cm, and the right one was an anechoeic mass of 7.3 · 6 cm. Tumor markers, Mantoux test, chest radiograph, and hydatid serology were normal. Because of the bilaterality, malignancy was suspected, and hence laparotomy was performed, which revealed a left-sided twisted hematosalpinx and a right-sided paraovarian cyst. Both ovaries were normal. Excision of the hematosalpinx and paraovarian cystectomy were performed. Histopathologic examination was consistent with left hematosalpinx, and the right paraovarian cyst was reported as serous cystadenoma. Results: The patient came for follow-up after 6 weeks and was happy to confirm the benign nature of her condition as was noted on the histologic report. Conclusions: The case illustrates bilateral adnexal masses of different etiologies that mimicked malignant ovarian tumors. Diagnostic laparoscopy may be performed to determine the correct origin of an adnexal mass, even if it is bilateral, in order to avoid laparotomy. ( J GYNECOL SURG 27:285)