The different schemes of application of gonadotrophin-releasing hormone (GnRH) antagonists in ovarian stimulation protocols for assisted reproduction are reviewed. Starting from the initial schemes of single and/or multiple doses, the efficacy of GnRH antagonists in 'soft' protocols of ovarian stimulation has been evaluated in natural cycles, and the possibility of inducing the final oocyte maturation under antagonists either with native luteinizing hormone-releasing hormone or with GnRH agonists. The largest clinical studies carried out with cetrorelix or with ganirelix and published to date were analysed. Apart from the benefits of reducing the duration of the treatment, gonadotrophin requirements and ovarian hyperstimulation syndrome incidence, there is still a serious debate on the potential deleterious effect of GnRH antagonists on implantation and pregnancy rates. More specific aspects such as cycle programming, application of GnRH antagonists in protocols for poor responders etc., were also reviewed in this survey.