Background: Herlyn-Werner-Wunderlich syndrome (HWW syndrome), is a rare congenital anomaly consisting of the triad of uterus didelphys, obstructed hemivagina, and ipsilateral renal agenesis. The diagnosis of HWW syndrome is often delayed because of less understanding of Müllerian anomalies by practitioners. Case: A 13-year-old female presented with severe dysmenorrhea. A diagnosis of HWW syndrome was confirmed by magnetic resonance imaging. Drainage of her hematocolpos was performed by resection of the vaginal septum. Laparoscopic fulguration of endometriosis lesions was performed; the lesions had been formed as a result of retrograde menstrual blood flow. Results: The patient's postoperative period was uneventful, and she was relieved of dysmenorrhea completely. After 2 years, she developed dysmenorrhea again as a result of restenosis of the septum and development of hematocolpos. Her vaginal septum was excised with suturing of the edges, and she was advised to retain her vaginal stent for 1 month. During a follow-up visit, this patient did not complain of dysmenorrhea and reported that she was having regular, normal menstruation. Conclusions: In young females presenting with intractable dysmenorrhea, a thorough evaluation should be conducted to rule out Müllerian anomalies. When an obstructive vaginal septum is excised for drainage of menstrual blood, it often becomes stenosed again, which may require a repeat excision and vaginal stent placement, thus, postoperative counseling and follow-up is very important. ( J GYNECOL SURG 32:54)