Objective: To describe a patient with recent onset of rapidly progressive virilization who was diagnosed with an androgen-secreting tumor of the left ovary, localized by selective ovarian vein catheterization and hormonal sampling (SOVHS). Design: Case report. Setting: Tertiary community-based medical center. Patient(s): A 32-year-old woman presenting with progressive virilization over a period of 4 months was found to have a Leydig cell tumor of the left ovary. Intervention(s): Transvaginal ultrasound of the pelvis, followed by contrast-enhanced computerized tomography of the abdomen and the pelvis. Selective ovarian vein sampling was performed to localize the tumor. Laparoscopic left salpingo-oophorectomy and washings were also performed. Main Outcome Measure(s): Initial serum total T levels were 1,505 ng/dL, and the free serum T levels were 234 ng/dL. After SOVHS, the total serum T levels in the left ovarian vein is reported to be 20,967 ng/dL, and in the right ovarian vein, they were reported to be 1,351 ng/dL. Three months after laparoscopic left oophorectomy, the serum total T levels were 11 ng/dL. Institutional review board approval was obtained. Result(s): Patient’ s ovarian tumor removed laparoscopically was reported to be a Leydig cell tumor. Rapid decreases in free and total T followed tumor removal. Conclusion(s): Selective ovarian vein catheterization and hormonal sampling is an effective diagnostic modality that can help localizesmall ovarian tumors. Objective: To describe a patient with recent onset of rapidly progressive virilization who was diagnosed with an androgen-secreting tumor of the left ovary, localized by selective ovarian vein catheterization and hormonal sampling (SOVHS). Design: Case report. Setting: Tertiary community- based medical center. Patient (s): A 32-year-old woman presenting with progressive virilization over a period of 4 months was found to have a Leydig cell tumor of the left ovary. Intervention (s): Transvaginal ultrasound of the pelvis, followed by contrast-enhanced computerized tomography of the abdomen and the pelvis. Selective ovarian vein sampling was performed to localize the tumor. Laparoscopic left salpingo-oophorectomy and washings were also performed. Main Outcome Measure (s): Initial serum total T levels were 1,505 ng / dL, and the free serum T levels were 234 ng / dL. After SOVHS, the total serum T levels in the left ovarian vein is reported to be 20,967 ng / dL, and in the right ovarian vein, they we re reported to be 1,351 ng / dL. Three months after laparoscopic left oophorectomy, the serum total T levels were 11 ng / dL. Institutional review board approval was obtained. Results (s): Patient’s ovarian tumor removed laparoscopically was reported to be Conclusion (s): Selective ovarian vein catheterization and hormonal sampling is an effective diagnostic modality that can help localizes mall ovarian tumors.