['The aim of the study was to compare the efficacy of half-dose, long-acting GnRH analogue (Diphereline) with Suprefact in IVF/ICSI (in vitro fertilization/intracytoplasmic sperm injection) cycles.', 'In this randomized clinical trial performed in Royan Institute, 126 infertile women who were first time candidates for IVF/ICSI were enrolled. Patients were randomly divided into two groups by using a random number table. In one group, 62 patients received a single half dose, 1.87 mg Diphereline, in mid-luteal phase. In the other group, 64 cases were treated with buserelin from the previous mid-luteal phase. P value less than 0.05 was considered significant.', 'The mean age of patients in the Diphereline and Suprefact groups was 27.9 ±3.6 and 29.6 ±3.5 years, respectively (p = 0.01). In the Diphereline group, the mean number of used gonadotropins was 25.6 ±12.1 ampoules, while in the second group it was 25.9 ±8.5 ampoules. Numbers of retrieved and MII oocytes were significantly higher in the Diphereline group (12.1 ±6.3 and 9.6 ±5.5) in comparison to the Suprefact group (9.4 ±6.4 and 7.2 ±5.1). Although the number of developed embryos in the Diphereline group was statistically higher than in the Suprefact group (6.1 ±3.9 vs. 4.7 ±3.4, p = 0.04) there was no significant difference in pregnancy rate (37.1%, 95% CI [26.16-49.54] vs. 37.5%, 95% CI [26.67-49.75]).'] Is half-dose , long-acting gonadotropin-releasing hormone agonist ( Diphereline ) comparable with daily injections of short-acting gonadotropin-releasing hormone agonist ( Suprefact ) in IVF/ICSI cycles?