In the past 20 years, a significant improvement has been shown in the treatment for infertility in both women and men through the development of in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI). Only donated sperm could be previously used for treatment, now oocytes can also be donated. Furthermore, the combination of IVF and ICSI with advanced genetic methods has made preimplantation genetic diagnosis possible for many genetic conditions. These methods enable genetic testing of the early human embryo by using only a single cell, one blastomere biopsied from the embryo, as the sample from which the diagnosis of many chromosome rearrangements and other inherited diseases can be made. It has also been established that a considerable proportion of infertility is caused by genetic defects, which have several implications for infertility treatment. The purpose of this review is to give a concise introduction on how genetics is involved in assisted reproduction technology to specialists who may not be working in this particular field of gynecology, but who would need some knowledge of this for proper care of their patients. © Acta Obstet Gynecol Scand (2005).