History and Objective: Ovarian hyper stimulation syndrome (OHSS) is a dangerous iatrogenic complication of ovulation induction cycles.Cconsidering HCC injection complications, reports of GnRH agonist effectiveness and safety in other countries and no report in Iran, in order to determine GnRH agonist effect on ovulation induction cycles in OHSS risk, this study was performed in Mirza Koochak Khan Hospital in 5004-2000. Considering HCC’s essential role in OHSS, in ovulation induction cycles with many follicle number and estradiol level elevation, HCC injection is not recommended. GnRH agonist was used for final oocyte maturation and ovulation stimulation in order to inhibit OHSS risk and

Material and Methods: A clinical trial was performed on women in ovulation induction cycle combined with IUI that were in OHSS risk. Patients were randomized in case and control group. Case group received GnRH agonist and the control group didn't. Progesterone levelwas measured on 21st or 23rd day of period cycle and was followed for ovulation, pregnancy and OHSS.

Results: 34 patients of total 70 that had suitable conditions were studied. Patients were matched for age and estradiol level. Ovulation rate in case and control group was 50% and 74/1%, respectively that was not statistically significant. There was no case of OHSS in both groups.

Conclusions and Recommendations: Results have revealed that GnRH agonist injection in hyper stimulated cycles will be successful and prevent OHSS. Therefore its application is recommended.