Objective: The aim of this study was to compare treatment outcome using GnRH-antagonist and hMG versus GnRH-a and hMG as controlled ovarian stimulation in IVF/ICSI cycles. The Hypothesis was to compare the efficiency of a new modality of controlled ovarian stimulation in IVF/ICSI cycles (GnRH-antagonist and hMG) compared to the use of GnRH-agonist and hMG. PATIENTS AND METHODS: One hundred couples were recruited from IVF unit Nile Badrawi Hospital during the period from May 2002 to November 2003. The patients were divided into two groups and Randomized by envelop seals. Group 1 included fifty patients who received Gonadotrophin releasing hormone agonist “long luteal protocol” + human menopausal Gonadotrophin. Group 2 included fifty patients who received Gonadotrophin releasing hormone (GnRH) antagonist + human menopausal Gonadotrophin. RESULTS: It was found that the duration of stimulation and number of HMG ampoules used were both significantly lower in the antagonist (group II). E2 level monitored in different opportunities during the stimulation cycle in both groups was significantly higher in the antagonist group. However, E2 done on day of ET was significantly lower in the antagonist group. At oocyte retrieval the number of oocytes retrieved was significantly lower in the antagonist group. More over the number of MII & cleaved oocytes (embryos) were significantly lower in that group. As regards the fertilization rate and quality of embryos no significant difference was found. The pregnancy rates were non-significantly lower in the antagonist group as compared with agonist. There was no statistical difference in spontaneous abortion rate and incidence of OHSS. The cost effectiveness analysis calculated in this study showed a statistically higher cost per cycle and cost per pregnancy while using the antagonist in comparison to the agonist. This result has a great impact on the patient where it may prevent some patients from having access to IVF/ICSI. COCLUSION: the use of GnRH antagonists is effective and safe comparable to the use of GnRH agonists. It is also tolerable with mild side effects at injection sites and no menopausal symptoms accompanying its use. It results in shorter duration of stimulation, and reduction of HMG use. However it can be demonstrated from the present series, the use of GnRH agonists is more cost effective whether in cost/cycle or cost/pregnancy. Larger multicenter controlled studies are required to confirm these results, and a search for more cost effective ovulation induction protocols using the antagonist is required in order to make its use the standard practice