It is well established that ovarian hyperstimulation syndrome (OHSS) is more frequent in patients with polycystic ovarian syndrome. In-vitro maturation (IVM) of immature oocytes presents a potential alternative for the fertility treatment and prevention of OHSS for these patients. This report describes the case of a 26-year old woman with a successful pregnancy and delivery following the transfer of frozen-thawed embryos derived from in-vitro matured oocytes. She had three failed cycles of ovarian stimulation (using low-dose step-up gonadotrophin protocol) with or without intrauterine insemination cycles, an ovulation-induction cycle with luteal long protocol, two fresh IVM cycle and one frozen-thawed IVM cycle. During the IVF cycle, she developed moderate OHSS and required hospitalization for 3 weeks. Following four unsuccessful IVF or IVM cycles, 15 months after the last cryopreservation, six fertilized oocytes were thawed for a scheduled embryo transfer. Following thawing, four fertilized oocytes survived and cleaved. Four frozen-thawed embryos were transferred. Six weeks after embryo transfer an ongoing intrauterine single pregnancy with fetal heartbeat was confirmed by transvaginal ultrasound. An uneventful pregnancy and delivery via Caesarean section at 39 weeks resulted in the birth of a normal healthy infant. (C) 2010, Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.