Objective: To develop exclusion testing protocols for Huntington’ s disease (HD) linkage markers suitable for use in a clinical preimplantation genetic diagnosis (PGD) setting for couples in whom a partner was at 50% risk of inheriting HD, but who choose not to undergo presymptomatic mutation testing. Design: Preimplantation genetic diagnosis using exclusion testing. Setting: In vitro fertilization clinic. Patient(s): Three couples with family histories of HD, two couples opposed to direct mutation testing. Intervention(s): Development of single- cell polymerase chain reaction tests for PGD for the HD mutation and two HD gene- flanking markers (D4S43 and D4S126), allowing the identification of an individual embryo as being at either lowor high risk for developing HD without being diagnostic of the presence of the mutation. Main Outcome Measure( s): D4S43, D4S126, and HD mutation. Result(s): After PGD for HD, couple 1 gave birth to a healthy girl after a frozen embryo transfer, and genetic status was confirmed by prenatal diagnosis to be very low risk for developing HD. Couple 2 gave birth to a healthy boy after their second cycle of PGD, and couple 3, after a third cycle, gave birth to a boy with congenital heart defects, which were successfully corrected with surgery at age 5 days. Both couples 2 and 3 declined prenatal testing, and therefore relinquished the opportunity to confirm the PGD. Conclusion(s): Preimplantation genetic diagnosis for HD using exclusion testing resulted in three live singleton births after six oocyte recovery procedures. The diagnostic protocol provided couples the opportunity to minimize the likelihood of disease transmission to their children, without the requirement for predictive testing. Objective: To develop exclusion testing protocols for Huntington’s disease (HD) linkage markers suitable for use in a clinical preimplantation genetic diagnosis (PGD) setting for couples in whom a partner was at 50% risk of inheriting HD, but who choose not to Design: Preimplantation genetic diagnosis using exclusion testing. Setting: In vitro fertilization clinic. Patient (s): Three couples with family histories of HD, two couples opposed to direct mutation testing. Intervention (s): Development of single - cell polymerase chain reaction tests for PGD for the HD mutation and two HD gene- flanking markers (D4S43 and D4S126), allowing the identification of an individual embryo as being at either lowor high risk for developing HD without being diagnostic of the presence of the Result (s): After PGD for HD, couple 1 gave birth to a healthy girl after a frozen embryo transfer, and gene Couple 2 gave birth to a healthy boy after their second cycle of PGD, and couple 3, after a third cycle, gave birth to a boy with congenital heart defects, which were successfully corrected with surgery at age 5 days. Both couples 2 and 3 declined prenatal testing, and therefore relinquished the opportunity to confirm the PGD. Conclusion (s): Preimplantation genetic diagnosis for HD using exclusion testing resulted in three live singleton births after The diagnostic protocol provided couples the opportunity to minimize the likelihood of disease transmission to their children, without the requirement for predictive testing.