GnRH agonist administration in the luteal phase was reported to beneficially affect clinical outcome of ICSI-ET cycles. This randomized controlled trial evaluates the effect of a single dose GnRH agonist administered in the luteal phase on the outcome of ICSI - ET cycles stimulated with the long GnRH agonist protocol. Women undergoing embryo transfer following controlled ovarian hyperstimulation with a long GnRH agonist protocol were included. In addition to routine luteal phase support with progesterone women were randomized to receive a single dose of GnRH agonist or placebo on the sixth day after ICSI.Ongoing pregnancy rate was the primary outcome measure.