To use preimplantation genetic diagnosis for achieving a polycystic kidney disease (PKD)free pregnancy for a couple in which the female partner was affected by PKD but whose PKD1 or PKD2 carrier status was not established. Case report. The IVF program of Reproductive Genetics Institute, Chicago, Illinois. An atrisk couple with the female partner affected by PKD, whose PKD1 or PKD2 carrier status was not established. Removal of PB1 and PB2 and testing for three closely linked markers to PKD1 (Kg8, D16S664, and SM7) and four closely linked markers to PKD2 (D4S2922, D4S2458, D4S423, and D4S1557) after standard IVF. Deoxyribonucleic acid analysis of PB1 and PB2 indicating whether corresponding oocytes were PKD1 or PKD2 allele free, for the purpose of transferring only embryos resulting from mutationfree oocytes. Of 11 oocytes tested by PB1 and PB2 DNA analysis, 7 were predicted to contain PKD1 or PKD2, with the remaining 4 free of both mutations. Three embryos resulting from these oocytes were transferred, yielding a twin pregnancy and the birth of two unaffected children. This is the first preimplantation genetic diagnosis for PKD, which resulted in the birth of healthy twins confirmed to be free of PKD1 and PKD2. Preimplantation genetic diagnosis based on linked marker analysis provides an alternative for avoiding the pregnancy and birth of children with PKD, even in atrisk couples without exact PKD1 or PKD2 carrier information. To use preimplantation genetic diagnosis for achieving a polycystic kidney disease (PKD)  free pregnancy for a couple in which the female partner was affected by PKD but whose PKD1 or PKD2 carrier status was not established. Case report. The IVF program of Reproductive Genetics Institute , Chicago, Illinois. An atrisk couple with the female partner affected by PKD, whose PKD1 or PKD2 carrier status was not established. Removal of PB1 and PB2 and testing for three closely linked markers to PKD1 (Kg8, D16S664, and SM7) Deoxyribonucleic acid analysis of PB1 and PB2 indicating whether oocytes were PKD1 or PKD2 allele free, for the purpose of transferring only embryos resulting from mutation  Of 11 oocytes tested by PB1 and PB2 DNA analysis, 7 were predicted to contain PKD1 or PKD2, with the remaining 4 free of both mutations. Three embryos resulting from these oocytes were transferred, yielding a twin pregnancy and the birth of two unaffected children. This is the first preimplantation genetic diagnosis for PKD, which resulted in the birth of healthy twins confirmed to be free of PKD1 and PKD2. Preimplantation genetic diagnosis based on linked marker analysis provides an alternative for avoiding the pregnancy and birth of children with PKD, even in atrisk couples without exact PKD1 or PKD2 carrier information.