Pituitary stimulation with pulsatile gonadotropin-releasing hormone (GnRH) induces both follicle-stimulating hormone and luteinizing hormone (LH). Blockade of pituitary gonadotropin secretion occurs upon desensitization when a continuous GnRH stimulus is provided by means an agonist or when the pituitary receptors are occupied with a competitive antagonist. The most common indication for blockade of pituitary gonadotropin secretion is with assisted reproduction treatment (ART) where it prevents premature luteinization. Originally by lack of clinically available GnRH antagonist, prolonged daily injection of agonist with its desensitizing effect was introduced for this purpose. Today, single- and multiple-dose injectable antagonists are also available to block the LH surge. This review provides an overview of the use of GnRH agonists and antagonists in assisted reproduction.