Context In reproductive-age women, one of the common adverse effects of chemotherapy and radiotherapy is premature ovarian failure. In addition, a significant number of women experience early menopause due to oophorectomy performed for benign indications. Objective To develop an ovarian transplantation technique to preserve endocrine function in women undergoing sterilizing radiotherapy and/or chemotherapy, or oophorectomy. Design and Setting Case study of 2 patients in New York who received autologous ovarian transplantation (patient A, November 1999; patient B, April 2000) to the forearm prior to pelvic radiotherapy or after oophorectomy. Participants Patient A is a 35-year-old woman with stage IIIB squamous cell cervical carcinoma and patient B is a 37-year-old woman with recurrent benign ovarian serous cysts. Main Outcome Measures Follicular development evident by ultrasound examination; cyclical production of estradiol and progesterone; restoration of serum follicle-stimulating hormone, luteinizing hormone, and testosterone levels to nonmenopausal range; and disappearance of menopausal symptoms. Results Menopause was confirmed immediately after the transplantation in both patients by serum follicle-stimulating hormone measurements (patient A, 47 mIU/mL; patient B, 50.7 mIU/mL). In patient A, follicle development was noted by physical and ultrasound examinations approximately 10 weeks after the transplantation. The mean (SE) follicle-stimulating hormone and luteinizing hormone levels decreased to 8.6 (0.4) mIU/mL and 12.8 (0.8) mIU/mL, respectively. The peripheral estradiol levels showed cyclical variation (mean [SE], 115 [9.2] pg/mL [422 {33.8} pmol/L), and during the 18-month followup, a dominant follicle developed each month. The estradiol levels from the right cubital vein were consistent with ovarian vein measurements (mean [SE], 1069 [269] pg/mL [3924 {987.5} pmol/L]). Percutaneous oocyte aspirations yielded a mature oocyte. In patient B, ovarian function was demonstrated by ultrasound visualization of a 9-mm follicle by 6 months after transplantation. Thereafter, the patient had spontaneous menstruation every 25 to 28 days. Ovulation was further confirmed by midluteal progesterone measurements (range, 7-10.1 ng/mL; mean [SE], 8.5 [0.9] ng/mL). Patient B's ovarian graft was still functional 10 months after the transplantation. Conclusions Subcutaneous ovarian transplantation appears to be a relatively simple, novel technique to preserve endocrine function in women undergoing sterilizing cancer therapy or surgery.