In the context of preimplantation genetic diagnosis (PGD), the quality system exists to ensure the quality of service that is the delivery of accurate and reliable genetic test results from human preimplantation embryos. In this chapter, these components are classified as follows: organization, personnel, facilities and safety, equipment, process control, process validation, documentation, adverse events, assessments, service and satisfaction, and process improvement. The chapter refers PGD as a process in combination with in vitro fertilization (IVF), involving the removal of one or two cells from an embryo and the subsequent testing of those cells for specific genetic disorders, characteristics, or chromosome number with a view to targeted embryo selection. It considers the individual components of the quality system with respect to the three phases of testing such as pre-analytic, analytic, and postanalytic. Finally, the chapter presents limited specific examples to illustrate some quality principles.