One of the most difficult aspects of assisted reproductive technology (ART) is the determination of which embryos are most suitable for transfer into the uterus. Two factors requiring consideration include the choice of embryos with the best developmental competence and the risk of multiple pregnancy associated with the number of embryos transferred. The development of technological advances such as micromanipulation and a wealth of experience in embryo culturing techniques have resulted in an increase in embryo implantation potential. Numerous criteria have been suggested to optimize the selection process. Despite all the advances in determining embryo developmental competence, no consensus has been reached on how many embryos to transfer. Key words: IVF, oocyte selection, embryo culture, PGD