This chapter considers ethical and legal aspects of preimplantation genetic testing, which includes both preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS). It first comments briefly on some of the objections presented by critics of PGD. The chapter next addresses some of the moral conditions for clinical PGD. It then focuses on some of the main ethical issues regarding PGD, more in particular on the debate about controversial indications. In the context of regular prenatal diagnosis, the principle of respect for autonomy is of utmost importance. The chapter further deals with a standard type of screening (screening for triploidy), an experimental one (screening for aneuploidy), and a possible future approach (comprehensive genetic screening). New technologies may permit genetic screening for nearly all chromosomal aberrations and many of the common Mendelian disorders and susceptibilities for complex disorders at once.