Objective: To develop and apply clinical preimplantation genetic diagnosis (PGD) for Marfan syndrome. Design: Case report. Setting: Centers for medical genetics and reproductive medicine in university hospitals. Patient(s): One couple in which the husband was affected with Marfan syndrome. Intervention(s): The couple underwent three intracytoplasmic sperm injection cycles. Main Outcome Measure(s): The correct diagnosis was obtained for embryos in three PGD cycles. Result(s): Although all the PGD cycles were followed by ET, no pregnancy ensued. Conclusion(s): This assay can provide a reliable and accurate preimplantation diagnosis of Marfan syndrome.