The primary aim of an in vitro fertilisation (IVF) treatment cycle is the creation of two 'good quality' pre-embryos for transfer, with a secondary aim of additional embryos for cryopreservation. The use of gonadotrophin releasing hormone (GnRH) agonists with gonadotrophins has resulted in greater ease of planning the superovulation stimulation. The move towards pituitary desensitization with a GnRH agonist has become almost universal in assisted conception clinics. The GnRH agonist is commenced in either the mid-luteal or follicular phase of the cycle and continued through to the day of human chorionic gonadotrophins (HCG). Modifications of the GnRH decapeptide have enabled the development of competitive inhibitors of gonadotrophin secretion. Clinical evidence followed in therapeutic trials for IVF suggests that recombinant-follicle stimulating hormone (FSH) yields more oocytes and embryos. Particular consideration needs to be given to superovulation when polycystic ovaries are present.