The in vitro fertilization technology coupled with the ability to amplify DNA from a single cell has been used for the preimplantation genetic diagnosis of Marfan syndrome. An intragenic FBN1 gene marker has been used to track the inheritance of this disorder in a family. Marker genotyping was established following two rounds of amplification. Whenever possible, two blastomeres were separately assayed per embryo. The transfer of five embryos resulted in a singleton pregnancy and the birth of a full-term male infant.