Abstract: The aim of this study was to investigate the outcome of frozen-thawed embryo transfer in exogenous estrogen plus progesterone without GnRH agonist and with GnRH agonist cycles for endometrial preparation in women with regular menstrual cycles. This study was designed as a prospective randomized clinical trial. In total, 60 patients were randomly divided into two treatment groups. In both groups, Estradiol Valerate was taken orally at 2 mg day-1 from day 1 to day 4, at 4 mg day-1 from day 5 to day 9 and at 6 mg day-1 from day 10 onwards up to the day of the pregnancy test. In day 13 of cycle, an ultrasound examination was performed. If the endometrial thickness was more than 8 mm, progesterone would be administered, i.m, at a dose of 100 mg day-1 and the dose of estradiol would be increased to 8 mg day-1 in all women if the endometrial thickness was less than 8mm. Group A (n = 30) commenced steroid supplementation without prior pituitary desensitization; whereas group B (n = 30) had pituitary suppression with using Busereline acetate (0.5 mg SC), a GnRH agonist, prior to steroid hormone administration that it was started in the mid luteal phase (day 21) of the menstrual cycle and was continued until day 11 of cycle. Present results showed that there was no significant difference in the woman`s age, duration and etiology of infertility, number of embryos transferred and the score of transferred embryos between the groups. The implantation rate, chemical and clinical pregnancy rates were 1.6, 10 and 6.6% in the group A and 3, 13.3 and 10% in the group B. There was no significant difference in implantation and pregnancy rates between both groups. In conclusion, endometrial preparation for FET based exclusively on steroid administration appears to be as effective as the protocol involving preliminary desensitization with a GnRH agonist.