Résumé : The purpose of this prospective study was to assess the reproductive outcome of patients with polycystic ovarian syndrome (PCOS) treated by in-vitro fertilization (IVF)/intracytoplasmic sperm injection (ICSI) with recombinant FSH (rFSH) and gonadotrophin releasing hormone (GnRH) antagonists. One hundred and ten patients were evaluated. The starting dose of rFSH was 100 IU in 67 women with body mass index (BMI) ≤29 kg/m2 and 200 IU in 43 women with BMI >29 kg/m2. GnRH antagonist was started by the detection of a follicle of ≥5mm in ultrasound scan. A significantly lower ongoing pregnancy rate per oocyte retrieval (25.6% versus 46.7%, P = 0.04) and a higher occurrence of ovarian hyperstimulation syndrome (16.3% versus 3.0%, P = 0.03) was observed in the group of patients with BMI >29 kg/m2 as compared with the group of patients with BMI ≤29 kg/m2, respectively. In conclusion, in GnRH antagonist cycles a worse reproductive outcome is expected in PCOS patients with BMI >29 kg/m2 in whom stimulation is initiated with 200 IU of rFSH as compared with PCOS patients with BMI ≤29 kg/m2 in whom stimulation is initiated with 100 IU of rFSH.