Preimplantation genetic diagnosis (PGD) is a complex process comprising many stages and involving a multidisciplinary team of healthcare professionals. PGD allows a couple to conceive pregnancy that is biologically their own and is unaffected by the genetic condition in the family. Embryos are created by using assisted reproductive technology (ART) and are tested for the relevant genetic condition by polar body, blastomere or trophectoderm biopsy. It is important to distinguish the difference between PGD and preimplantation genetic screening (PGS) for sporadic chromosome aneuploidy. PGS is distinct from PGD and it is mainly used within the ART arena as an adjunct to fertility treatment with the aim of improving in vitro fertilisation (IVF) outcome. The potential use of PGD to select embryos with desirable nonmedical traits such as intelligence, beauty or longevity perhaps represents a more distant future for PGD.