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Background&Objective: Up to seventh week of gestation, progesterone secreted from the ovary is necessary to preserve the pregnancy. In the ART cycles GnRH-a is prescribed and oocytes and granulosa cells or retrieved, both causes corpus luteum insufficiency, so corpus luteum should be supported the best way is progesterone prescription. In this research we compare intramuscular and intravaginal suppositoar forms of progesterone for preserve the pregnancy. Materials&Methods: A prospective cross sectional evaluation on 193 patients was designed. All of them were on IVF or ICSI cycles. The patients were randomly divided into two groups. Intramuscular progesterone was prescribed in 138 and intravaginal progesterone (supp cyclogest) in 54 patients. The outcome of pregnancy was analyzed using statistical trials including t-test and chi-squre. Results: The two groups were similar duo to age – the ethiology causes of infertility – the doses of proscribed HMG ampule – FSH titrago – the number and grade of transferred embryos. The day after HCG presciption until the end the seventh week in the first group (138 patients) intramuscular progestrone (50 mg /bid) and in the secound group (54 Patients) supp of cyclogest (400 mg / bid) was prescnbed. The rate of positive pregnancy test, abortion, successful poegnancy in this two groups were similar. Conclusion: Intramuscular or intravaginal progesterone for supporting corpus luteum in IVF or ICSI cycles has the same effect but the intramuscular route is cheaper.