Maternal age has been considered a major determinant for the success of assisted reproduction treatment. Women experience a sharp decline in fecundity after the age of 40 due to decreasing oocyte competency and ovarian function. While the correlation between fecundity and age in women in their 30s and early 40s has been extensively studied and well established, there is no clear data on younger patients’ conception through the assisted reproduction. The objective of this study was to determine whether young age (less than 25 years) has an impact on outcome where the cause of infertility is male factor or in egg donation cycles. A retrospective study in a university affiliated tertiary care facility. The study was conducted with patients undergoing IVF-ET in our clinic from 1994 to 2005. Seventy-four women less than 25 years of age with 80 cycles (group I) underwent IVF-ET. The control groups consisted of patients between 25 and 34 (n = 115, group II) and 35 - 39 (n = 83, group III) enrolled for IVF-ET treatment at the same time. Controlled ovarian stimulation was performed using the long luteal phase GnRH-agonist protocol, and 10,000 IU hCG was given for the final stage of follicular maturation. Oocytes were retrieved 34-36 hours after administration of hCG and underwent either insemination or ICSI. Normal fertilization (2PN) and embryo development were assessed and embryos that had cleaved to the two-cell stage or further were identified and graded using criteria based on blastomere number, symmetry, and degree of fragmentation. Embryo transfer (ET) was performed 72 hours post retrieval. When available, only embryos of the highest quality at the 6-8-cell stage were transferred. A pregnancy test was performed 14 days after ET. Clinical pregnancy was defined as a gestational sac within the uterus on ultrasound. Data were obtained from 360 cycles of IVF / ICSI (Table I). Each group was compared in terms of embryo development, embryo quality, average number of embryos transferred, and chemical or clinical pregnancy. For each patient there was at least one excellent grade embryo to transfer. There were no significant differences between the number of mature oocytes (MII), fertilization rate, and the quality of the embryos transferred. However the number of oocytes retrieved, fertilization rate following IVF and ICSI, and positive β-hCG were lower, although not significantly so, in younger patients. The clinical pregnancy rate was significantly lower in the young patients compared to the other two groups.Tabled 1 Our results demonstrating lower pregnancy rates in young patients compared to the patients in their thirties were surprising. Since a sufficient number of embryos of good quality were available for transfer in all women, the significantly lower pregnancy rate in younger patients or donors is puzzling. However, these findings are consistent with the prior observation that some young egg donors have a high percentage of aneuploid embryos.