OBJECTIVE To examine the effect of GnRH analogue (GnRH-a) on the quality of frozen-thawed embryos and the pregnancy rate (PR) resulting from transfer. METHODS A retrospective study of two groups of women undergoing transfers of frozen-thawed embryos. In group 1 ovulation induction with hMG was begun after hypophyseal desensitization with GnRH-a for 2 weeks. In group 2 ovulation was induced with hMG only. The freezing and thawing techniques were identical for both groups. METHODS In vitro fertilization unit at a university hospital. METHODS The study group (group 1) included 108 women who underwent 137 transfer cycles of frozen-thawed embryos, and the control group (group 2) included 44 women in 51 cycles of thawed ETs. METHODS Ovum pick-up and ET techniques were the same for both groups. Methods of embryo freezing and thawing were identical, as were the morphological criteria for grading the embryos. RESULTS The morphology of embryos was similar in both groups, as was the number of embryos that had at least 50% intact blastomeres (83% +/- 23% and 78% +/- 30% for group 1 and group 2, respectively). The PR (16 of 137 [11.7%] and 6 of 51 [11.8%], respectively) as well as the abortion rate (30%) were similar for both groups. CONCLUSIONS The use of GnRH-a does not affect the quality of embryos nor the pregnancy outcome. Because the yield of frozen embryos per ovum pick-up is higher in cycles stimulated by GnRH-a/hMG, the PR per pick-up cycle is thus anticipated to be higher.